UNBiology1

School Science Lessons
Biology experiments
Updated: 2008-03-01
Biology names

Table of contents
9.0.0 Plant kingdom, plantae
9.39.0 Algae
9.46.0 Liverworts, hornworts, mosses
9.48.0 Ferns, club moss. palms
9.51.0 Flowering plants (angiosperms)
9.60.0 Heterotrophic angiosperms
9.54.0 Plant cells and tissues
9.65.0 Leaves
9.71.0 Roots
9.78.0 Stems

9.0.0 Plant kingdom, plantae
9.39.0 Algae (seaweed, waterweed)
9.46.0 Liverworts, hornworts, mosses
Liverworts, Phylum Hepatophyta (Hepaticae) Marchantia, Riccia
Mosses, Phylum Bryophyta (Musci) Dawsonia, Funaria
9.48.0 Ferns and club moss
Ferns, true ferns, Phylum Pteridophyta (Pterophyta, Filicales) Dryopteris, Pteridium
Club mosses, Phylum Lycopodiophyta (Lycophyta, Lycopodiales) Lycopodium, Selaginella
Horsetails, scouring rushes, Phylum Equisetophyta (Equisitales, Equisetopsida, Sphenophyta) Equisetum arvense
Whisk ferns, Phylum Psilophyta (Psilotales) Psilotum, Tmesipteris
Seed-bearing plants (Spermatophyta)
Conifers, cone-bearing trees, Phylum Pinophyta (Coniferophyta, Pinopsida, Coniferales) gymnosperms, Pinus
Ginkgo, Maidenhair tree, Phylum Ginkgophyta (Ginkgoales) gymnosperms, Ginkgo biloba
Gnetophytes, Phylum Gnetophyta (Gnetopsida, Gnetales) gymnosperms, Ephedra, Gnetum, Welwitschia
Cycads, Phylum Cycadophyta (Cycadales) gymnosperms, Cycas, Macrozamia
Glaucophytes, Phylum Glaucophyta, unicellular, freshwater flagellates, Glaucocystis
Hornworts, Phylum Anthocerotophyta, Anthoceros
9.51.0 Flowering plants (angiosperms)
9.51 The parts of a flowering plant
9.52 Monocotyledons, grasses, orchids, lilies palms, bulbs, corms, rhizomes, Dendrobium, Spinifex, Iris
9.53 Dicotyledons, herbs, shrubs and trees Ranunculus, Solanum
Heterotrophic angiosperms, Dipodium, Drosera

9.39.0 Algae
9.1.0 Algae classification (seaweed, water-weeds)
9.39 Chlamydomonas, Sphaerella (Haematococcus)
9.40 Pleurococcus (Protococcus)
9.41 Spirogyra, Zygnema
9.42 Volvox
Green algae, Phylum Chlorophyta, desmid
9.43 Closterium
Brown algae, brown seaweed, kelps, Phylum Phaeophyta
9.44 Ecklonia
9.45 Hormosira
Oedogonium
9.9.5a Vaucheria
9.9.6 Fucus, Ecklonia, brown seaweed, kelp
Unicellular algae, Chlamydomonas, Euglena, Pleurococcus (Protococcus), Sphaerella (Haematococcus), Desmids: Ceratium, Closterium, Diatoms
Filamentous algae, Cladophora, Oedogonium, Oscillatoria, Spirogyra, Ulothrix, Zygnema, Blue-green algae: Nostoc
Brown algae, Ecklonia, Fucus, Hormosira, Red algae: Dictyota

9.46.0 Liverworts, hornworts, mosses
9.46 Marchantia
9.47 Dawsonia

9.48.0 Ferns, club moss. palms
9.48 Dryopteris
9.49 Selaginella
9.50 Conifers
9.50 Conifers, Pinus
6.27 Describe palms (Primary)
6.28 Describe ferns and mosses (Primary)

9.51.0 Flowering plants (angiosperms)
9.51 The parts of a flowering plant
3.25 Parts of a plant (Primary)
9.52 Monocotyledons
9.53 Dicotyledons
1.4 Different plants (Primary)
1.5 Plant pictures (Primary)
1.26 Plant names (Primary)
6.23 Trees and shrubs (Primary)
6.24 Trees, palms and ferns (Primary)
6.25 Protect our trees (Primary)
6.26 Describe grasses (Primary)
6.27 Describe palms (Primary)
6.28 Describe ferns and mosses (Primary)

9.60.0 Heterotrophic angiosperms
9.6.1 Bird's nest orchid Neottia
9.6.2 Insectivorous plants, pitcher plant Nepenthes, Venus fly trap Dionaea
9.6.3 Sundew, Drosera
9.6.4 Butterwort, Pinguicula
9.6.5 Bladderwort, Utricularia
9.6.6 Parasitic angiosperms, toothworts, broomrapes, mistletoe, sandalwood, devil's twine, Olax, North American pitcher plant Sarracenia.
9.6.7 Dodder (Cuscuta), mulberry mistletoe (Loranthus), parasites
9.6.8 Mycorrhizal plants, Dipodium, Eriostemon, pine tree Pinus

9.54.0 Plant cells and tissues
9.0.1 Characteristics and functions of plant tissue types
9.0.2 Plant Tissues
9.9.0 Cells, human cheek cells, plant cells, Elodea
9.9.1 Staminal hair cells, Tradescantia, cells from multicellular organisms
9.9.2 Cell walls and plasmolysis, Elodea
9.9.3 Onion leaf scale cells, onion leaf epidermis, bulb
9.9.4 Plant epidermis, Tradescantia, Zebrina
9.9.5 Subsurface sections of leaf, Vinca
9.9.7 Stone cells, pear
9.9.8 Examine pond weed, Elodea
9.54 The plant cell, cork cells, Robert Hooke
9.55 Human cheek cells
9.56 Leaf scale cells of onion
9.57 Cells and tissue sections, T.S., L.S., R.L.S., T.L.S
9.58 Parenchyma cells of tomato
9.59 Phloem cells of pumpkin
9.60 Section cutting
9.61 Microscope staining techniques
9.62 Stamen hair cells of Tradescantia
9.63 Cells of a waterweed, Elodea
9.64 Wood cells, Eucalyptus, poplar
2.30 Rub leaf pictures (Primary)
2.35 Paint with plant juices (Primary)
3.30 Make plant dyes (Primary)

9.71.0 Roots
9.3.3 Root hairs, bean, maize (corn)
9.66.2 Young root of black mustard, white mustard
9.3.5 Roots of cress, garden cress and mustard
9.3.6 Lateral roots, cress, coconut
9.3.7 Dicotyledon root, broad bean, buttercup
9.3.9 Mycorrhizal roots, birch, pine, heather Calluna, bird’s nest orchid Neottia
9.3.12 Storage roots with food reserves
9.3.15 Root pressure, Fuchsia stem, busy Lizzie
9.3.16 Tap roots, wallflower, groundsel
9.3.17 Adventitious roots, twig of the willow
9.3.18 Climbing adventitious roots, ivy
9.3.19 Specialized roots, prop roots, tap roots, tuberous roots
9.71 Dicotyledon root and monocotyledon root
9.72 Legume roots, broad bean, clover, Rhizobium
9.73 Apogeotropic roots of mangrove
9.74 Excretion of acids by roots
9.75 Root hairs of a germinating bean
9.76 Root structure of mung bean
9.77 Root function, Tradescantia
1.29 Roots and stems (Primary)
5.30 Roots absorb water (Primary)

9.78.0 Stems
9.57.4 Stem with secondary thickening, linden tree (lime tree), horse chestnut
9.4.5 Stem of lucerne, herbaceous stem
9.4.6 Stem of Dianthus, herbaceous stem
9.4.7 Stem of Iris, herbaceous stem, monocotyledon
9.4.8 Stem of Spinfex, xeromorphic stem
9.4.9 Tissues in stalk of bean or celery stalk (petiole)
9.4.12 Twigs of trees in winter, horse chestnut, sycamore, lime tree (linden tree), beech, oak
9.4.13 Terminal bud, linden tree (lime tree), beech, oak
9.4.14 Creeping stems, moneywort, creeping Jenny, ground ivy
9.4.15 Runners, strawberry
9.4.16 Stolons, currant, gooseberry, banana
9.4.17 Woody stem, hawthorn
9.4.18 Stem hooks, bramble, rose
9.4.19 Twining tendrils, white bryony, passionfruit, sweet pea, garden pea
9.4.20 Herbaceous stem, buttercup
9.4.21 Twining stem, climbing bean, yam
9.4.22 Corm, false stem (pseudostem) banana, taro
9.4.23 Rhizome, ginger, tumeric
9.78 Celery stalk
9.79 Dicotyledon stem, sunflower, Helianthus
9.80 Monocotyledon stem, maize (corn), Zea
9.80.1 Other monocotyledon stems
3.28 Stems and roots (Primary)

9.65.0 Leaves
9.65 Leaf of a bushy plant
9.66 Leaves of agricultural plants
9.67 Grass leaf
9.68 Eucalyptus leaf, isobilateral leaf
9.69 Stomates in a leaf
9.70 Leaf with aerenchyma, water lily
9.5.1a Leaf, external features of a leaf, elm, beech, apple, Hydrangea
9.66.3 Leaf, structure of dicotyledon leaf, privet, lilac
9.69.1 Leaf, Structure of stomata, Eucalyptus, Hakea, iris, privet, narcissus, water lily
9.5.4 Leaf, stomate, apple, adaptations of stomates
9.5.5 Leaf tendrils, garden pea, sweet pea
9.5.6 Leaf, foliage leaves, stipules
9.82 Leaf of Hakea, xeromorphic leaf
9.5.10 Leaf of water lily, hydrophyte leaf, water hyacinth (noxious weed)
9.5.11 Phylloclades, butcher's broom
9.5.12 Phyllode, Acacia
9.5.13 Cladode, Bossiaea, See diagram 9.53.6
1.6 Different leaves (Primary)
3.26 Different leaves (Primary)
3.27 Describe leaves (Primary)
5.31 Leaves lose water (Primary)

9.1.0 Algae (seaweed, water-weeds)
The term "algae" is still used but it is not so popular nowadays. Classify most of the types of algae within the Protista because they are largely single celled organisms, diatoms, chrysophytes, or if multicellular they show little differentiation of cell types. Blue-green algae are now called cyanobacteria. They are prokaryotic and are really a form of bacteria that happens to contain chlorophyll and is thus photosynthetic. Being photosynthetic no longer determines whether you classify an organism as a plant. The following may be classified as "photosynthetic protists":
1. Blue-green algae (Cyanobacteria, Cyanophyta) Oscillatoria
(Anabaena can fix atmospheric nitrogen and lives in leaf cavities of the floating fern, Azolla, to be an important source of nitrogen fertilizer for the rice industry in Vietnam and China.) (thermophilic cyanobacterium Mastigocladus laminosus lives in hot springs.) (Nostoc lives in the roots of Cycas.) (Spirulina is used as a food and health drink.)
2. Green algae, Chlorophyta, Chlamydomonas | Cladophora | Closterium (a desmid), Eudorina, Gonium, Oedogonium, Pandorina, Pleodorina, Pleurococcus (Protococcus), Sphaerella (Haematococcus)| Spirogyra (Zygnema) | Ulothrix, Ulva (sea lettuce) | Volvox
See 9.9.4: Chloroplasts of Spirogyra and Ulothrix
3. Red algae (coral algae), Rhodophyta, Corallina, Nemalion, Polysiphonia, Porphyra, Rhodolith (Chondrus and Gigartina contain carrageenan.), Dinoflagellates, Phyrrhophyta, dinophyta (plankton) (Ceratium colours the upper ocean red.) (Noctiluca causes bioluminescence.) (Gymnodinium causes red tide.) zooxanthellae in corals
4. Euglena group, Euglenophyta, Euglena
5. Chara group (stoneworts), chlorophyta, charophyceae (The musk grass Chara has a musky, earthy odour and looks like a higher plant), Nitella
6. Brown algae, Phaeophyta (Alginates are used to thicken ice cream.), Dictyota | Fucus | Ecklonia | Oedogonium | Hormosira | Vaucheria
Examine filaments under low power, then examine a cell in detail under high power. Look also for oogonia and antheridia. Examine a prepared slide showing dwarf males.

9.9.5a Vaucheria
Mount some fresh filaments. Observe the method of branching. Examine part of a filament under high power. Examine a prepared slide showing antheridia and oogonia.

9.9.6 Fucus, Ecklonia, brown seaweed, kelp
See diagram 9.44: Ecklonia seaweed
1. Examine a brown seaweed found between low and high tide marks. Observe the holdfast for anchorage, the stem and the expanded frond containing chlorophyll for photosynthesis and the yellowish pigment fucoxanthin. Examine a plant of Fucus as an example of a brown seaweed. Observe the disc shaped or branched holdfast, the stalk or stipe, and the expanded lamina showing thick midrib and wings. Note also the indentations at the tips of the thallus where the growing points are situated.
2. Observe the holdfast, stipe and fronds. If the specimen is Fucus vesiculosus, note also the bladders that give buoyancy. Cut a transverse section across a vegetative branch and mount and examine under low power. Note the differentiation into limiting layer, cortex and medulla. Examine prepared slides of transverse sections cut through male and female conceptacles. Observe the antheridia, oogonia and paraphyses.

9.1 Liverworts, Pellia
1. Collect plants of Pellia in the early spring. Observe the leafy gametophyte with rhizoids at its base and the capsule or sporogonium. Note the presence of dark green globular capsules just behind the growing points of some thallus branches. Also, note small warty prominences further back from the tip and either side of the midrib. These prominences are old antheridia cavities, now empty. Dissect out a sporogonium, noting the short seta. Crush the capsule into a drop of water. Observe the wall with its characteristic thickenings, the spores and the elaters. Cut a transverse section of the thallus, mount in water and note the structure, similar to the lamina of Fucus but attached to the soil with hair-like rhizoids.
2. Collect Pellia plants in the early summer. Observe the presence of antheridia and cut sections through the thallus where they occur. Note also involucres just behind the tips of some branches and cut longitudinal sections through these to see the archegonia.

9.2 Mosses, Funaria
See diagram 9.47.1: Funaria, sporogonium | See diagram 9.51.2: Moss life cycle
In open country, moss grows mostly on the north side of trees in the northern hemisphere and on the south side of trees in the southern hemisphere.
Examine capsules of Funaria or other mosses at different stages of maturity and note the peristome and the method of liberation of spores. If you fix a cut off capsule in wax, you can examine the peristome under low power. Breath on the capsule to show the hygroscopic movements of the peristome teeth.

9.3 Mosses, Polytrichum
Collect protonema from hedgerows or on the soil in flower pots. Polytrichum spores germinate to form a filamentous stage called a protonema. Later, buds form on the protonema to grow into the moss plant. Polytrichum often mingles with Vaucheria, but Polytrichum is septate. Observe the green filaments with transverse septa and the brownish rhizoids with oblique septa. Observe buds on the green filaments and young plants in various stages of development.

9.48.1 Ferns, true ferns, Phylum Pteridophyta (Pterophyta, Filicales) Pteridium
See diagram 9.48.1: Fern leaves Pteridium | See diagram 9.48.2: Pteridium frond, rhizome | See diagram 9.48.3: Pteridium prothallus, sporophyte
1. Dehiscence of fern sporangia Pteridium
Scrape some ripe sporangia into a drop of glycerine on a slide. The glycerine withdraws water from the annulus cells and thus causes the opening of the sporangia. You can slow the movements of the annulus with glycerine. Scrape other sporangia on to a warm slide and observe the annulus movements under the microscope.
2. Fern prothallus Pteridium
To grow fern prothalli, place a soaked flower pot inside a larger one, packing the space between with wet sphagnum or peat. Allow a mature frond bearing a sorus to dry on a piece of paper and then scatter the spores so obtained on the inner surface of the small flower pot. Stand the pots in an inch or so of water and cover the top of the pots with a sheet of glass. Green prothalli will soon appear, and you can observe successive stages in their development. Observe the archegonia and also the liberation of sperms from the antheridia. Young sporophytes will develop if you water the prothalli after they show archegonia.

9.48.2 Club mosses, Lycopodium
In Lycopodium clavatum note the presence of definite cones. Examine the sporangia, both externally and by cutting sections of the cones.

9.4.0 Seed-bearing plants (Spermatophytes, seed plants)
9.4.0.1 Naked seed plants (Gymnosperms, ovules and seeds on surface of leaf-like sporophylls), cycads, conifers, Pinus, Ginkgo
9.4.0.2 Cycads, burrawang palm, cardboard palm, sago palm, fern cycad, prickly cycad (large palm-like with trunk covered with leaf bases)

9.4.1 Conifers, Pinus, spruce, larch, redwood, podocarp, hoop pine, juniper (cone-bearers)
See also: 3.21.5 Conifers, Phylum Pinophyta
See diagram 9.4.1: Pine cone
1. Examine twigs of Pinus in summer. The twigs should show evidence of at least three years' growth. Observe the structure of purely vegetative twigs, the position and structure of seed cones of varying age, the position and structure of staminate cones.
2. Dissect first year, second year and third year seed cones and note their general structure. Note the seeds lying naked on the cone scales.
3. Remove a megasporophyll from a first year cone and look for the two megasporangia (ovules) on the upper surface. The bract scale is on the lower surface.
4. Examine the structure in longitudinal section under high power.
5. Examine a sporophyll from a second year cone in the same way.
6. Examine a third year cone. Remove a megasporophyll and note the seeds with their wings attached. Cut a longitudinal section through a seed and examine under low power.
7. Dissect a staminate cone and note the form of the microsporophylls (stamens). Crush one of them into a drop of glycerine and examine the pollen grains under high power. Examine transverse and longitudinal sections of staminate cones.
8. Examine the structure of the current year stem and the older stems by means of transverse and longitudinal sections. Examine the tracheids, the sieve tubes, the medullary rays and the resin canals.
9. Cut a transverse section of a leaf, noting the particulars described in the text.

9.5.1 Monocotyledons and dicotyledons

Monocotyledons	Dicotyledons
Embryo has one cotyledon	Embryo has two cotyledons
Mostly herbaceous plants, except palms	Mostly woody plants
Tap roots are common	Tap roots are rare
Vascular bundles closed, cambium absent, secondary thickening rare	Vascular bundles open, cambium present, secondary thickening common
Leaves have parallel veins with simple cross connections, midrib is absent	Leaves have network of veins, midrib is present
Floral parts usually in threes, typical floral formula: P 3+3 A 3+3 G3.	Floral parts usually in fives, typical floral formula: K5 C5 A5 G5
Include grasses, orchids, lilies, palms. Many have bulbs, corms, rhizomes	Most trees and shrubs

9.9.0 Cells, human cheek cells, Elodea plant cells
See diagram 9.56.1: Cell walls | See diagram 9.9.5a: Plant cell, cell wall and cell membranes
Plant and animal cells are similar, consisting of a protoplast bounded by a cell membrane. Plant cells have a rigid cellulose wall surrounding the protoplast. The cell wall is in contact with its cell membrane. Mature plant cells have vacuoles and plastids. Plastids are membrane bound organelles in the cytoplasm. The three types of plastids are as follows: 1. Chloroplasts contain chlorophyll pigments and occur in all green parts of the plant. 2. Chromoplasts contain carotene and xanthophyll pigments. They give colour to all red, orange and yellow parts of the plant. The pink, purple and blue colour of plants come from anthocyanin pigments dissolved in the vacuole sap, e.g. Tradescantia, beetroot. 3. Leucoplasts are colourless plastids found in most other plant cells where starch grains may form as a storage product, potato Solanum tuberosum.

9.9.1 Staminal hair cells, Tradescantia, cells from multicellular organisms
See diagram 9.178: Plasmolysis in Tradescantia cells
1. Use plasmolysis to show that the cell wall is a non-living envelope distinct from the cytoplasm. Irrigate the preparation with a hypertonic salt solution more concentrated than the cell sap. By osmosis, water passes from the weaker solution to the stronger solution through the differentially permeable living cell membranes. The resulting contraction of the living cell contents is called plasmolysis. In the plasmolysed cell, the cell wall that is permeable to the solution remains rigid. The salt solution remains in the space between the cell wall and protoplast. If you then irrigate the preparation with water the protoplasts expand again quite rapidly as water passes in through the living membranes of the cytoplasm to the vacuole. The original state of turbidity of the cells returns.
3. To study the differentially permeable membranes, irrigate the preparation with iodine to kill it and again attempt plasmolysis with hypertonic salt solution. The cell no longer responds because the differentially permeable properties of the cytoplasmic membranes have died. A mature plant cell with vacuoles has two cytoplasmic membranes. The outer membrane is in contact with the cell wall. The inner membrane separates the vacuole from the cytoplasm. Use iodine solution to stain the nucleus.

9.9.2 Cell walls and plasmolysis, Elodea
See diagram 9.63: Cell, waterweed, Elodea cell
1. Examine the small leaves near the end of the stem of the waterweed Elodea. Put a single small leaf in a drop of water on a glass microscope slide, cover with a coverslip and examine with a microscope. In strong light the cellular contents may have a flowing motion called cytosis or protoplasmic streaming.
2. Make a slide of living Elodea to show the presence if a cell wall. Put a drop of salt water solution on one edge of the coverslip. Draw the salt solution under the coverslip by placing a piece if absorbent towelling or blotter at the opposite side of the slip so that the liquid on the slide will rise up the paper. Water will diffuse out of the cells into the salt water. As this proceeds, the cellular contents may be observed to shrink, but the rigid cell walls retain their original structure. Other plant cells may be used to show this phenomenon. Fleshy leaves that have a thin layer which can be peeled off are possible sources of thin cellular layers.
3. Repeat the experiment with Tradescantia, lettuce and spinach cells.

9.9.3 Onion leaf scale cells, onion leaf epidermis, bulb
See diagram 2.30: Detach epidermis from leaf

9.9.4 Plant epidermis, Tradescantia, Zebrina
See diagram 9.69.3 Stomate, surface view, guard cells | See diagram 9.65.3.1: Section view of a leaf | See diagram 9.69: Stomate guard cells
1. Use a razor blade to make an incision on the under surface of a Tradescantia leaf and strip off a small section of epidermis. Mount outer surface uppermost in water. Tradescantia has no stomata in the upper epidermis. Observe the following: 1. The guard cells that should be open if the weather is bright. 2. The extra thickening on the walls of the guard cells is next to the pores. 3. Accessory cells surround the guard cells. 4. The larger epidermal cells have colourless plastids. Guard cells have chloroplasts but epidermal cells do not. Leucoplasts (colourless plastids) cluster around the nucleus of the accessory cells.
2. Plants possess a skin called the epidermis. To study the epidermis of the leaf of a trailing plant, transfer a drop of water from a beaker to a microscope slide with a glass rod. Stretch a trailing plant leaf, with the lower surface facing upwards, over the index finger of the left hand, holding it in place with the middle finger. Make a small cut on the surface of the leaf with a dissecting needle. Grasp the torn edge with pointed forceps and peel off a small piece of the epidermis of the lower surface of the leaf. Put it, with the external surface upwards, in the drop of water on the slide. Mount a coverslip. Examine the slide under low power. Note the shape of the epidermal cells and the bean shape cells, which always lie together in pairs, called "guard cells". A stomate is this pair of cells and the opening between them. Most of the water lost by the plant, and all the exchange of gases takes place through these stomates. The guard cells of the stomates may be surrounded by four cells that differ from that of the other epidermal cells. This group of six cells is called a stomatal apparatus. Find a stomatal apparatus. Examine the slide under high power. Note the stomatal apparatus and the epidermal cells surrounding it. Note which epidermal cells contain chlorophyll grains (i.e. have chloroplasts). Observe the cell nuclei.

9.9.5 Subsurface sections of leaf, Vinca
Use a variegated leaf of Vinca to cut thin subsurface sections just below the upper and lower epidermis. To do this, hold a leaf over your index finger and anchor it with your thumb and third finger. Observe the following: 1. The upper epidermal cells and the tops of the palisade cells. The air spaces between palisade cells are small in diameter but extend vertically through the tissue. Mount this section with epidermis uppermost. 2. The lower epidermal cells and part of spongy mesophyll cells with large air spaces. Mount this section with the spongy mesophyll uppermost.

9.9.7 Stone cells, pear
See diagram 9.78.4: Stone cells
Pull apart the gritty tissue of pear fruit on a slide. Examine the structure of the stone cells. Note the absence of cytoplasm and look for simple unbranched and branched pits. Stain with iodine solution or aniline sulfate or aniline chloride to show the lignified walls.

9.9.8 Examine pond weed, Elodea
Mount a complete leaf of Elodea in water on a slide and examine under high power of the microscope. Note the small green granules containing chlorophyll, chloroplasts. Observe the movement of the chloroplasts showing that the cytoplasm is moving, cytoplasmic streaming. Note the cellulose cell walls.

9.3.3 Root hairs
See diagram 9.75: Root hairs on germinating bean seed | See diagram 9.73.3: Root hairs in the soil | See diagram 9.73.2: Root hairs in L.S root
1. Root hairs increase the surface area of the roots and usually occur in very large numbers. Maize, Zea mays has 420 root hairs per mm². Leave cress, garden cress seeds, Lepidium sativum, to swell in water in a flat glass dish for 15 minutes. Cut a square of filter paper from a sheet and wrap around a glass plate and hold in place with rubber bands. Transfer swollen cress seeds with forceps to the filter paper and put in two rows, each row 3 cm from the edge of the two narrow ends. Because their coats are mucilaginous, the seeds stick well to the paper. The glass plate is placed in a 400 mL beaker, water is added until the level almost reaches the lower row of seeds. The beaker is then covered with a Petri dish and left to stand. Within three days small cress seedlings have developed from the seeds. The roots of the bottom row which are dipping in the water have almost no root hairs. The roots of the upper row growing in air on the moist filter paper have formed a large number of hairs. The roots on the lower row have formed few roots.

9.66.2 Young root of black mustard, white mustard
Cultivate mustard seed on damp absorbent paper. Use a hand lens or low power of a microscope to see the cylindrical radicle, the root cap and the root hairs. Cut off the radicle then cut it longitudinally down the middle and mount in water. Observe a single mature hair. It is an outgrowth of an epidermal cell.

9.3.5 Roots of cress, garden cress and mustard
1. Soak a ceramic flower pot in water and scatter the cress seeds thinly over the inner surface. They stick to the pot because of their mucilaginous seed coats. Invert the pot over a dish containing enough water to cover the rim of the pot and put in a warm place. The seeds will quickly germinate and provide suitable roots for examination. Cut off the terminal 1 cm from the end of one root and mount in lactophenol-erythrosin. Note the arrangement of tissues at the apex, the region of elongation, the development and structure of root hairs. After making these observations, crush the specimen and examine the older region for annular and spiral vessels of the protoxylem.
2. Germinate mustard seedlings on damp absorbent paper and cover with a glass jar. Cut transverse sections: 1. 1 mm behind tip for apical meristematic cells and root cap cells 2. 2 to 4 mm behind tip for elongating cells and 3. 6 to 8 mm behind tip for elongated cells and root hairs. Stain in acid phloroglucin and mount in 50% glycerine solution.

9.3.6 Lateral roots, cress, coconut
See diagram 53.5: Lateral roots of coconut
Allow cress seedlings or other seedlings to grow until the radicle shows lateral roots. Cut off the radicle just above the smallest visible laterals and mount this terminal length in lactophenol-erythrosin, coiling it round if necessary. Note the stages in the development of the lateral roots. Coconuts have no root hairs.

9.3.7 Dicotyledon root, broad bean, buttercup
See diagram 9.73.1: Root types | See diagram 9.73.2: Root L.S. | See diagram 9.73.3: Root in soil | See diagram 9.72.2: Root transverse sections, TS
1. Cut a transverse section of a broad bean root. Use the thumb and forefinger to hold the root between two pieces of pith or carrot tissue. Dip the material in water to moisten it. Never cut dry material! To cut microscope sections use a one-sided razor blade, "Gem", dipped in water. Hold the material vertically and draw the razor blade quickly across it. Cut the thinnest possible sections as wedge shapes. Wash the sections into a small dish of water. Use a camel hair paint brush to select the thinnest section, mount it in water on a slide and cover with a coverslip. Irrigate with aniline sulfate to colour the xylem elements yellow. Look for the following tissues all embedded in parenchyma. Note the relative positions of the various tissues. Examine the tissues under high power and note the cellular structures:
1.1 the piliferous layer, with its root hairs,
1.2 the cortex, composed of the cortex proper and the endodermis,
1.3 the stele, composed of xylem (protoxylem and metaxylem), phloem and pericycle.
2. Cut a transverse section of a buttercup root. Note the creeping stems and the adventitious roots arising at nodes from stems. Observe the epidermis, wide cortex containing parenchyma, and the endodermis that is the innermost layer of the cortex. The endodermis forms a definite ring of thickened cells. See the passage cells through the endodermis opposite the protoxylem. The phloem and xylem are exarch, i.e. the first cells to differentiate are towards the outside of the stele. The xylem consists of four protoxylem groups linking with the metaxylem that occupies the centre. In the root, the first cells of the xylem to become fully differentiated, i.e. lignified, are those cells towards the outside of the core of xylem. This part of the xylem, differentiated while the root is still elongating, is the protoxylem. Metaxylem is the remainder of the xylem to differentiate after the root stops elongating. Protoxylem and metaxylem together form the primary xylem. Primary xylem and primary phloem are both derived directly from the provascular tissue.

9.3.9 Mycorrhizal roots, birch, pine, heather
Mycorrhiza roots are found growing in the surface layers of leaf mould below the trees. Note the characteristic branching. Cut sections of leaf mould to see ectotrophic mycorrhiza. Collect young, thin roots of heather in the spring. Mount a length of one of them in lactophenol-erythrosin and look for endotrophic fungal threads in the narrow cortex. Examine a section of heather root to see endotrophic mycorrhiza.

9.3.12 Storage roots with food reserves
See diagram 9.85: Potato tuber
Test plant organs for glucose and fructose, seeds, leaves, roots, stems, tubers.

9.3.15 Root pressure, Fuchsia stem, busy Lizzie
See diagram 9.184: Root pressure
Do NOT use elemental mercury for school experiments!
1. Cut a Fuchsia stem. Cut the stem of a single stem pot plant 1 cm above the soil. Fit a short piece of rubber tubing to the cut stump then fill the tubing with water. Insert into the end of the rubber tubing 50 cm of narrow bore glass tubing. Fix the glass tubing vertically and each day measure the height of liquid in it. Replace the glass tubing with a manometer and record the root pressure attained.
2. The salt concentration of the cell sap in both the root hairs and root cells is generally higher than that of their surroundings. Consequently, because of the semipermeable nature of the cell membranes, water is absorbed by osmosis through the root and rises in the plant under a certain pressure. This root pressure maintains the turgor of plant tissues. Cut a busy lizzie or a Fuchsia, horizontally, 5 cm above the soil. Apply glycerine around the outside of the stump. Fix a piece of rubber tubing over it and bind with string. Connect a glass tube, 400 mm long, to the other end of the rubber tubing and hold it in place with a small clamp and a right angle clamp attached to a Bunsen burner stand. Attach a scale to the glass tube. Pour water into the tube so that its level can be read against the scale. Covert the tube with liquid paraffin to prevent evaporation from the surface of the water. Add water to the pot regularly and read the level of the water meniscus in the glass tube. The meniscus slowly rises in the glass tube.

9.3.16 Tap roots, wallflower, groundsel
See diagram 9.73.1: Two kinds of roots
Any grass has fibrous roots. Watercress has adventitious roots. In dicotyledons, the main axis of the root (tap root) grows vertically downwards and is continuous with the stem. It bears lateral branch roots that originate from within the root tissue. The tip of each root has a growing apex protected by a root cap. Several centimetres behind the apex is a mass of root hairs growing out from the surface layer of the root. These increase the surface area of the roots where water absorption occurs. In monocotyledons, grasses, the fibrous root system with no obvious tap root. There are many roots of about equal size and most of them arise from the lower part of the stem at nodes (adventitious roots). The shoot system consists of a stem with long leaves attached at nodes. The leaves have no petioles, but have long sheathing leaf bases that in the young plant enfold the younger leaves. At the top of the sheathing leaf base there may be a small membranous tongue, the ligule, a common feature of grasses. The lamina is long and linear with parallel venation.

9.3.17 Adventitious roots, twig of the willow
Observe the development of adventitious roots on the twig of the willow. Gather the twigs late in the winter and place in water. In a few weeks, the buds will open and adventitious roots will appear on the stem. Keep a dated record of the progress of the shoot.

9.3.18 Climbing adventitious roots, ivy
Detach a spray of ivy from an old wall or the trunk of a tree. Note how difficult doing this without breaking the stems of the ivy is because the adventitious roots cling to their support. Examine these adventitious climbing roots.

9.3.19 Specialized roots, prop roots, tap roots, tuberous roots
See diagram 9.87: Sweet potato tuber
1. Prop roots holds up the stem, maize (corn)
2. Swollen tap roots store food, radish.
3. Tuberous roots store food, sweet potato

9.57.4 Stem with secondary thickening, linden tree (lime tree), horse chestnut
See diagram 9.57.4: Tilia TS Stem
1. Examine transverse sections through the stem of various ages as follows: 1. near the apex of the shoot 2. the middle of the first year's growth 3. near the bottom of the first year's growth 4. about the middle of a later year's growth. Note the secondary wood and examine the vessels of the spring and autumn wood. Look for medullary rays. On the outside of the cambium, note the secondary phloem, containing thickened cells called phloem fibres. Note how the medullary rays widen out in the phloem. Near the periphery, look for cork cambium, and note the layers of cork cells produced on the outside of this.
2. Examine a secondarily thickened stem by means of radial longitudinal and tangential longitudinal sections. Observe the following tissues:
2.1 The periderm consists of phellem and phellogen. Phellem (cork) cells have radial rows of cells with suberized walls, formed by division of the phellogen (cork cambium), one row of radially flattened cells with thin walls. In some plants the phellogen may also produce a farther layer, the phelloderm, towards the inside. This layer is not apparent in Tilia. The lenticels, part of periderm, are regions of rounded, loosely packed cells, which allow exchange of gases through the otherwise impermeable tissue
2.2 The secondary phloem, in wedges, consists of alternating bands of fibres and sieve tubes, companion cells and parenchyma.
2.3 The cambial zone
2.4 The secondary xylem
2.5 Primary rays extend from the cortex to the pith and are very wide in secondary phloem.
2.6 Secondary rays are in secondary xylem and phloem and do not extend to the centre or to the cortex.
2.7 Primary xylem surrounds the medulla. The interpolation of secondary vascular tissues between primary xylem and primary phloem creates considerable stress in the stem.
3. The medulla and primary xylem are least affected. In the outer layers, accommodation to the increasing circumference is accomplished by the following changes:
3.1 The epidermis initially keeps pace with growth by radial cell divisions but eventually is replaced by a periderm of superficial origin, usually just beneath epidermis.
3.2 The cortex increases in circumference by expansion of cells in the tangential plane, and divisions in the radial plane. Parenchyma is mostly squashed, but collenchyma retains its form and the new walls from recent cell divisions are evident.
3.3 Parenchyma cells of the primary rays between phloem wedges expand and divide similarly. Some of these rays become conspicuous by great increase in width towards the periphery.

9.4.5 Stem of lucerne, herbaceous stem
Herbaceous stems have growth from the cambium limited to one season or part of one season, or lacking. They have no distinctive anatomical structure, but some features are typical of monocotyledons others of dicotyledons. Vascular bundles in stems are collateral with endarch xylem. Lucerne is a perennial herbaceous plant grown for fodder.
Observe the following tissues:
1. The epidermis is covered by a cuticle.
2. The cortex is narrow compared with the cortex of the root and consists of collenchyma as four corner strands forming longitudinal ridges on the stem and parenchyma.
3. The outer part of the cortex contains chloroplasts.
4. The single peripheral ring of discrete bundles without active cambium.
5. The vascular tissue arranged as discrete collateral bundles with phloem to the outside, xylem to the inside and cambium between the xylem and phloem.
6. The pith consisting of parenchyma in the centre of the stem.
7. The parenchyma rays between the vascular bundles.

9.4.6 Stem of Dianthus, herbaceous stem
Dianthus is a perennial herbaceous plant with a complete vascular cylinder. Observe the following: epidermis covered by a cuticle, cortex comprising chlorenchyma and sclerenchyma, stele is a continuous ring comprising phloem, cambium, xylem, endarch (the first formed xylem next to the pith), medulla parenchyma.

9.4.7 Stem of Iris, herbaceous monocotyledon
Observe the widely spaced discrete vascular bundles arranged peripherally in two rings or scattered throughout the transverse section. Cambium is not usually formed and most vascular bundles have a sclerenchyma sheath. In monocotyledons with scattered bundles there is no distinction of ground tissue into cortex and medulla. Where the vascular strands are confined to the periphery of the stem there is either a medulla cavity or a distinct parenchyma medulla.

9.4.8 Stem of Spinfex, xeromorphic stem
Spinfex is a grass that grows on sand dunes. It has a prostrate stem with roots and shoots at the nodes. The anatomical structure is a typical monocotyledon stem with scattered bundles and no cambium. Observe the following: epidermis covered by cuticle, vascular bundles scattered throughout the parenchyma ground tissue, a fibre sheath around each vascular bundle, a continuous band of sclerenchyma in the peripheral region where the sheaths merge to give rigidity to the stem.

9.4.9 Tissues in stalk of bean or celery stalk (petiole)
See diagram 9.78.3: T.S. Bean stem

9.4.12 Twigs of trees in winter, horse chestnut, sycamore, lime tree (linden tree), beech, oak
See diagram 9.51.2: Horse chestnut shoot
Note the terminal bud, the leaf scars with associated axillary buds, the ring of bud scale scars and the lenticels. Dissect a terminal bud. Arrange the scales and young foliage leaves in series. The scales are leaf bases. A large scar between two terminal buds shows the position occupied by an inflorescence in the previous spring. The formation of an inflorescence by the terminal bud leads to the growth of the branch being carried on by the two axillary buds immediately below. Examine stages in the opening of the buds in spring.

9.4.13 Terminal bud, linden tree (lime tree), beech, oak
Examine the apparently terminal bud and note that at the side of a leaf scar another small scar has been formed by the withering and falling off of the original terminal portion of the shoot. So the apparently the terminal bud is really an axillary bud. Dissect a bud and arrange the parts in a series. Note the pair of outer scales followed by pairs of inner scales that have a small foliage leaf between them. The bud scales are stipules. Note the opening of the buds in the spring and note that the stipules soon fall from the foliage leaves.

9.4.14 Creeping stems, moneywort, creeping Jenny, ground ivy
Note the long, recumbent habit of the stem, the absence of scale leaves and the position of the adventitious roots.

9.4.15 Runners, strawberry
Study the formation of new plants. The short stem, the crown, produces runners, stolons, from it axillary buds. The stolons are modified shoots. The second node on the stolon touches the ground and forms a new plant.

9.4.16 Stolons, currant, gooseberry, banana
See diagram 51.13.1: Banana stool
Note the curved stems and how adventitious roots are given off from where the stem touches the ground. Note exactly where the new adventitious shoots form.

9.4.17 Woody stem, hawthorn
See diagram 9.57.2: Piece of cut wood | See diagram 9.57.1: Wood sections
Stems have four functions: 1. Transport of food from leaves to roots 2. Transport of water and plant nutrients from roots to leaves 3. Support of leaves and branches 4. Store food.
Note the position of the thorns on the hawthorn stem. Look also for larger examples, which bear foliage leaves. Compare the structure of a twig of gorse with that of the hawthorn.

9.4.18 Stem hooks, bramble, rose
Examine the hooks on the stem and petioles of the bramble or rose. Compare them with thorns. Hooks are modified hairs. Thorns are modified branch shoots.

9.4.19 Twining tendrils, white bryony, passionfruit, sweet pea, garden pea. (Virginia creeper has adhesive tendrils.)

9.4.20 Herbaceous stem, buttercup
See diagram 9.51: Ranunculus buttercup
Cut by hand TS and LS sections of young buttercup stems.

9.4.21 Twining stem, climbing bean, yam
See diagram 63.5: Yam growth, Yam tuber
Swollen rounded underground stem, i.e. stem tuber, e.g. yam.

9.4.22 Corm, false stem (pseudostem) banana, taro
See diagram 51.5: Banana corm | See diagram 51.1: Banana false stem | See diagram 62.7: Taro corm | See diagram 9.82: Gladiolus corm
1. The true stem of the banana plant is an underground stem, a rhizome. The swollen stem base is the corm with very short internodes. The corm makes shoots that grow into branches or other corms. New plants come from these shoots. Suckers grow from the dormant buds called "eyes" on the corm. Each sucker formed is higher than the corm it came from. If the land is sloping, the suckers are usually formed on the uphill side. If left alone, generations of banana plants will gradually move up a hill.
2. The taro corm is an underground stem swollen with stored starch. Like other stems it has these parts: The growing point or a shoot apex. Many leaves joined to the shoot apex. Leaf scars are seen as circular marks that go around the corm. Axillary buds form just above the place where the leaf was joined to the stem. The axillary buds can grow into little corms or "cormlets" (cormels). The cormlets can grow into suckers.

9.4.23 Rhizome, ginger, tumeric
See diagram 9.83: Ginger | See diagram 9.83.1: Iris rhizome
The ginger rhizome is hard and compressed sideways. Inside it is pale yellow. It is covered with scales and has fine fibrous roots.

9.5.1a External features of a leaf, elm, beech, apple, Hydrangea
See diagram 9.66
Choose a simple form of leaf and examine its external appearance in detail. Note the leaf, showing the swollen leaf base, the petiole and the lamina. Examine the type of venation, and note how the veins gradually diminish in size, until the ultimate branches are scarcely visible.

9.66.3 Structure of dicotyledon leaf, privet, lilac
See diagram 9.65.7: Privet leaf
1. Choose a part of a leaf which contains some of the midrib. Fix it between two pieces of elder pith or carrot so that you can cut the midrib transversely. Mount the section and stain with an aniline salt. Examine the structure under the low power, noting the upper epidermis covered with a layer of cuticle, palisade tissue, spongy tissue, and lower epidermis covered with a slightly thinner layer of cuticle. Note also the vascular bundle forming the midrib, composed chiefly of xylem and phloem. Note the midrib embedded in a sheath of parenchyma cells and the thin portion of the leaf. Note the absence of chloroplasts in the upper and lower epidermis, a large number in the palisade mesophyll cells and a relatively smaller number in the spongy mesophyll cells. Note the shape and position of the chloroplasts. Examine the shape of the cells of the palisade tissue and note the number of layers here. The cells are separated by small air spaces. Note the irregular shape of the spongy mesophyll cells and the air spaces between them. Privet is a mesophyte dicotyledon with dorsi-ventral leaves.
2. Observe the following: 1. The upper epidermis with stomata, cuticle and glandular hairs. 2. The palisade mesophyll consisting of vertically elongated cells with chloroplasts. 3. The spongy mesophyll consists of loosely packed cells with air spaces and chloroplasts. 4. The lower epidermis has stomata, cuticle and glandular hairs. 5. Small lateral veins, often cut obliquely during preparation of the microscope slide, are situated between the palisade and spongy mesophyll. 6. The midrib is a continuation of vascular tissue of the leaf stalk. In the midrib vein, the xylem is uppermost and the phloem is on the underside.

9.69.1 Structure of stomata, Eucalyptus, Hakea, iris, privet, narcissus, water lily
See diagram 9.65.3.1: VS Leaf | See diagram 9.69.2: Surface view and section view of a stomate | See diagram 9.69.3 Surface view Guard cells | See diagram 9.69.1: Hakea stomate
1. Chose a small portion of the leaf, and tear off the epidermis as a thin layer. Mount the piece of epidermis flat in water and examine it under high power. Examine a stomate and surrounding cells as a small pore surrounded by two kidney shape guard cells. The guard cells usually contain chloroplasts but epidermal cells do not usually contain chloroplasts. While looking at a stomate irrigate with salt solution and see the guard cells become plasmolysed closing the pore of the stomate.
2. Cut a transverse section of the leaf and look for a stoma cut in section. Notice the shape of the guard cells and of the pore itself. Note also the large air space in the mesophyll immediately adjoining the stomate pore.

9.5.4 Leaf, stomate, apple, adaptations of stomates
1. Iris and Narcissus have an isobilateral monocotyledon leaf with palisade tissue on both surfaces. The thickness of the cuticle varies on different leaves of the same plant. However, plants adapted to dry conditions, Hakea and Eucalyptus, have thick cuticles and plants growing with abundant water supply, Nymphaea, water lily, have thin cuticles.

9.5.5 Leaf tendrils, garden pea, sweet pea. (Yellow vetchling has stem tendrils.)
Note their position and relation to other leaf structures.

9.5.6 Foliage leaves, stipules
See diagram 9.66.2: Different leaves | See diagram 9.48.1: Stipules | See diagram 52.2: Breadfruit stipules | See diagram 53.3: Coconut leaf
Note the stipules of certain leaves in rose, pea. Note net venation (reticulate venation) and parallel venation in grasses. Leaves adapted for photosynthesis have the following features: 1. The broad leaf blade, lamina, has a large surface area to volume ratio and many stomata, pores, to help light absorption and gas exchange. 2. Many vein endings supply water and remove sugar from the leaf.

9.82 Leaf of Hakea, xeromorphic leaf
Many species of Hakea have needle-shaped leaves in which there is a reduction in leaf surface/volume ratio. Observe the following: 1. epidermis with thick cuticle and sunken stomates 2. palisade mesophyll cells in a double layer interspersed with sclereids 3. central storage mesophyll with scattered vascular bundles.

9.5.11 Phylloclades, butcher's broom
Note the very reduced leaves that are modified branches.

9.5.12 Phyllode, Acacia
See diagram 9.53.5: Acacia
Note the buds or branches in the axils of the phyllodes showing that these are modified leaf structures

9.6.1 Bird's nest orchid Neottia
Note the matted underground stems and the fleshy roots. Sections of the latter will show the endotrophic mycorrhiza.

9.6.2 Insectivorous plants, pitcher plant, Venus fly trap
See diagram 9.66.3: Nepenthes
Butterworts and sundews live on wet acid soils where there is a lack of nitrogenous compounds. Keep plants damp in the laboratory with the original soil left around the roots.

9.6.3 Sundew, Drosera
Drosera rotundifolia occurs in bogs. Observe the creeping rhizomes, rosette arrangement of the leaves and short petioles. In the field, touch the leaf to get the tentacles to respond as if trying to trap an insect. Mount tentacles and examine under low power. Note the stalk and the glandular head.

9.6.4 Butterwort, Pinguicula
Note the rosette leaves with incurved margins of the butterwort and the sticky nature of the upper surface. Mount a piece of leaf with the upper surface uppermost and examine under low power. Note the stalked capturing glands and the sessile digestive glands.

9.6.5 Bladderwort, Utricularia
The bladderwort lives in pools of brackish water. This plant has no roots. The leaves are very finely divided. The flowers project above the water. Note the shape of the bladder and the presence of hairs at the orifice. Open several bladders and look for the remains of animal prey.

9.6.6 Parasitic angiosperms, toothworts, broomrapes, mistletoe, sandalwood, devil's twine, Olax, Sarracenia
Rafflesia has the largest flower in the world.
See diagram 9.53.11: Mulberry mistletoe, Loranthus
See sections across a branch in TS or LS and through the haustorium longitudinally. Greenhouses of botanic gardens often contain examples of tropical carnivorous plants

9.6.7 Dodder, Cuscuta
See diagram 9.53.12: Dodder haustorium penetrating host Mistletoe
Observe dodder plants coiling around the stems of clover, heather, gorse and nettle, Urica. Note the manner in which it coils around its host, its reduced, scale-like leaves and its pink flowers. Notice the absence of chlorophyll and explain the parasite's method of nutrition in view of this. Examine the haustoria and cut a transverse section of the stem of the host plant in the region of a haustorium. Notice the type of host tissue that the haustoria cells penetrate.

9.6.8 Mycorrhizal plants, Dipodium, Eriostemon, Pinus
The mycelia of certain fungi assist in absorbing of plant nutrients, especially poor soils. The relationship between the fungus and the plant is mutualism. Some fungi live just outside the roots of woody species, e.g. Eucalyptus, oaks, pines, olives. Other fungi penetrate the root and live between the cells in many grain plants.

9.0.1 Characteristics and functions of plant tissue types

Tissue system	Tissue types (numbered)	Characteristics	Function
Meristematic tissues	1. Apical meristems 2. Cambium	Closely packed cells with large nuclei and thin walls	Produces new cells by cell division
Ground tissues	3. Parenchyma: Unspecialized ground tissue especially cortex and pith	Living protoplasts, cells loosely packed, thin cellulose walls with simple pits 3a. Chlorenchyma has chloroplasts for photosynthesis 3b. Aerenchyma has large intercellular spaces for internal aeration	Packing tissue, lateral transport, mechanical support by turgidity in herbaceous plants, cells can divide after wounding and production of cambium
"	4. Collenchyma: Subepidermal or cortical in stems and leaves only	Living protoplasts, cells elongated, primary cellulose walls with thickened corners, simple pits.	Supporting tissue in strands or cylinders subepidermal in stems, petioles and leaf veins.
"	5. Sclerenchyma: Fibres in stem cortex and leaf mesophyll tissue and sclereids scattered in parenchyma	Cells with thick lignified walls, dead at maturity. 7. Fibres are interlocking elongated and narrow cells. 8. Sclereids have variable size and shape.	Strengthening tissue of root, stem and leaf. Fibres in strands or cylinders in cortex. Small groups of sclereids in parenchyma of soft leaves and fruits, or massed to form stony tissue of fruits
Dermal tissues	6. Epidermis: Layer covers primary body of plant	One cell in thick with cutin on outer wall. Stomata (pores) on aerial plant parts	Protective and prevent desiccation in stem and leaf Stomata allow gas exchange. Epidermal root hairs increase water uptake
"	7. Periderm: External covering replaces epidermis in secondary body	Phellem (cork): Layers of cells produced outside by cork cambium (phellogen), protoplast dead at maturity, walls impregnated with suberin	Protective waterproof layer replaces epidermis in older stems and roots. Lenticels on stems have function of stomata.
Vascular tissues	Xylem: Consists of vessels, tracheids, fibres and parenchyma cells.	Vessels: Tubes formed by dissolution of the end walls of a vertical column of cells. Wall have lignin and bordered pits, except in protoxylem, no protoplast at maturity	Water conduction through long continuous tubes. Protoxylem annular and spiral thickenings allow extension of vessels (and tracheids) in regions of elongation
"	"	Tracheids: Elongated lignified cells with complete end walls, have bordered pits except in protoxylem, no protoplast at maturity	Water conduction through pits in walls, or through non-lignified areas of walls as in protoxylem spiral and annular tracheids
"	"	Xylem fibres: Like fibres of sclerenchyma	Strengthening but not conducting
"	"	Xylem parenchyma: Parenchyma in vertical columns, walls sometimes lignified	Food storage
"	"	Xylem ray parenchyma: Formed from ray initials of cambium, radially elongated	Radial conduction of food and water across xylem
"	Phloem: Consists of sieve tubes, companion cells, fibres, parenchyma and ray parenchyma	Sieve tubes: Vertical rows of elongated cells with perforated end walls called sieve plates, have cytoplasm but no nucleus at maturity	Conduction of organic food materials
"	"	Companion cells: Elongated cell has with nucleus and dense cytoplasm, and is with a sieve tube element, many mitochondria	Control of sieve tube
"	"	Phloem parenchyma: Vertical files of parenchyma	Storage of foods, tannins and resins
"	"	Ray parenchyma: Formed from ray initials of cambium, radially elongated	Radial conduction across phloem
"	"	Phloem fibres: Like fibres of sclerenchyma	Strengthening

9.0.2 Plant Tissues
See diagram 9.53: Plant parts
The tissues are formed by groups of cells that have similar or related functions. In multicellular plant bodies the cells are cemented together where adjacent cell walls touch by the middle lamella that may contain calcium pectate. Where the walls are not in contact, the spaces between them form a continuous intercellular system of air spaces. This can be very extensive in parenchyma tissues, or absent in conducting tissues. The plasmodesmata, fine cytoplasmic connections through minute pores in walls of adjacent cells, maintain continuity of the cytoplasm. When the walls become thickened, these connections are often lost. Pits, or thin areas in cell walls, are sometimes associated with plasmodesmata. In many differentiated cells, the cell walls become thick and impregnated with other substances and the protoplast disappears at maturity. These non-living units are still called cells. They function in conduction of materials (xylem), provide mechanical strength (fibres) or give protective covering (cork and bark). Tissue arrangement is different in animals where the cells have no walls and are embedded in a matrix secreted by the cells. This matrix is often extensive and lacks an air space system such as is found in plant tissues. A plant tissue may be simple or complex. A simple tissue is a group of structurally similar cells of similar origin and performing the same function, parenchyma (storage and packing), collenchyma (mechanical), sclerenchyma (mechanical). A complex tissue is a group of dissimilar cells of similar origin performing the same function, vascular tissue of the xylem containing: vessels, fibres, tracheids, and parenchyma cells.