Plants and their ways in South Africa

Front matter

22102057233

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EDMONDS’ (H.) ELEMENTARY BOTANY, adapted for South Africa. New Edition (1903), thoroughly revised by Dr. Marloth and J. Bretland Farmer, D.Sc,,

Introduction

With the introduction of microscopes into the secondary schools, the early superficial study of plant “ analysis,” which aimed at finding the names of plants, gave place to a study of minute anatomy and the lower forms of plant life. The microscopical method is of undoubted educational value, but the student, who confines his attention too exclusively to minute structures and forms of plant-life, is in danger of losing that living interest which a wider outlook into the science alone can afford.

There is yet a third method which considers plants as living things, and the study of their life relations becomes the new standpoint from which they are approached. The influence of light, air, and moisture on the form and position of stems and leaves, and how the conditions of soil affect the development and distribution of plants, are questions not only of interest in themselves, but likely to stimulate the reasoning powers of even young children ; and children are most interested when they can be led to think for themselves.

This book has been written with a view to suggesting how some of these conditions are met by plants in South Africa. Some of the chapters, as, c.^., IV., VII., and XVIII., are intended as reading lessons. The object of others is to furnish outlines for the study of plant forms, while there is vni

Introduction little, except, possibly, the names of the parts of the flower in Chapter XhV., which should be committed to memory.

Plants can he brought to the schoolroom and studied in window-boxes. It is not enough to see the plants through the stage of germination merely; they should be watched until their life story has been told.

With the generous aid of the Education Department, it is possible to add each year some simple, well-constructed apparatus as a means of increasing interest in the work. It is poor economy to use implements so crude as to give inexact and unsatisfactory results, when, for a slight outlay, the correctness and consequent value of an experiment may be insured. Glass jars, flasks with rubber stoppers, retort stands, porous flower-pots of various sizes, wire, thread, scissors, cork-borers, glass and rubber tubing, U-tubes, glass funnels, and thermometers are indispensable.

Valuable suggestions may be obtained from Prof. Atkinson’s “ First Studies of Plant Life,” from the “ Elementary Textbook,” by Prof. L. H. Bailey, and the accompanying Lessons, the Plant Physiologies of Darwin and Acton, MacDougal, and Ganong. “ The Teaching Botanist,” by Ganong, and “ Plant Geography,” by Schimper, are excellent books. “ Flowering Plants and Ferns,” by J. C. Willis, of the Cambridge Biological Series, is a valuable guide in the study of morphology, geographical and economic botany. To this list may be added Maud Going’s charmingly written book, “ With the Trees and with the Wild Flowers.”

My thanks are due to the generous advice and assistance rendered by Dr. Marloth, Dr. MacOwan, Dr. Bolus, and the Rev. Dr. Kolbe.

It is also a pleasure to express my deep indebtedness to my present and former students who have kindly assisted me in illustrating the book, in particular to Miss Lucette Creux

Introduction

IX and Miss Hannah Albertyn for the illustrations furnished by them, and to Miss Ethel M. Doidge for those bearing her initials, to Miss A. V. Duthie for numerous drawings, and to the untiring interest of Mrs. G. A. Bottomley, to whom the greater number of the original pen-and-ink drawings are due.

The author is indebted to the publishers (Messrs. Longmans, Green, and Co.) for the privilege of using from Edmonds and Marloth’s “ Elementary Botany of South Africa,” Rev. Prof. Henslow’s “ South African Flowering Plants,” Thome and Bennett’s “ Structural and Physiological Botany,” and Farmer’s “ Practical Introduction to the Study of Plants,” the illustrations acknowledged in the text.

This work is the second of “ The South African Science Series,” the first being Mr. Rogers’ “ The Geology of Cape Colony,” designed by Dr. Muir to promote the study of natural science in South Africa.

Huguenot College, Wellington,

South Africa,

February, 1906,

Contents

CHAPTER page

I. Plant Life i

II. Seeds and their Germination 6

Chapter I Plant Life

Who has not watched and enjoyed growing things ? The baby is carefully weighed and measured; the kitten, the garden, and the flowers of the veld in turn absorb our attention.

Growth means life ; and every living thing has something of interest to tell if our eyes have been trained to see and we have learned to think about what we see.

In studying plants we find great differences in the plant kingdom, and how as living things they can change their form and habits of growth so as to fit themselves to widely differing conditions of life, for plants cannot choose where they would grow. In doing so, the members of one plant family come to look so unlike one another that it becomes difficult to detect any family resemblance ; while members of different families look enough alike sometimes “ to be brothers and sisters,” for plants that have come from the same parents in past years are grouped together in a family or order.

We are surprised to find that dodder, which fastens its threads upon lucerne and chokes it and robs it of its food,

belongs to the highly respectable family of the sweet potato.

When lavish Nature sows her seed, some, it is true, “ fall upon stony places and wither away,” but some lay hold of the

B rocks and change them into soil, so that one dainty pink-andwhite Crassida which grows on our hillsides rejoices in the name Saxif'aga, the rock breaker.

It would be difficult to say where plants are not found ; on the heights of the Drakensberg, and even higher ranges, flowers blossom and die, where no eyes but their Maker’s behold their beauty. Plants are found, beautifully white and delicate, deep down in the darkest mines. They are able to withstand the heat of boiling springs, and explorers from the frozen Antarctic return with mosses and lichens. Germs of plants kept in liquid air for six months at a temperature of — 190° have suffered

no injury, while others have remained for ten hours in a bath of liquid hydrogen, 60'’ colder still, and have then come forth and flourished.

Plants are quite at home on cheese and canned fruit, and an old shoe cast upon a refuse-heap may boast its botanic garden. These are the moulds, and against them the housekeeper is waging constant warfare.

Some plants are so small that the sharpest eyes cannot see them without powerful microscopes. Of these, some grow in the human body better than anywhere else. We call them germs. Several kinds grow on the teeth and cause their decay, unless the teeth are carefully brushed. One kind, which passes part of its life in impure milk or water, lodges in the throat and causes diphtheria ; and another produces enteric fever, so that eternal vigilance is the price of health.

Others of these minute plants are as useful as some are harmful. When the housekeeper is mixing “ sponge ” for bread, she is putting in as she stirs germs known as yeast

Fig. I. — Common mould {Mucor juucedo) • I. An entire plant with six sporangia in different stages of development (strongly magnified). IT. Single sporangium with spores 1) (X200). (From Thome and Bennett’s “Structural and Physiological Botany.”)

Plant Life plants. It th6 sponge is set in a warm place, the moisture causes them to grow rapidly. The growth changes a part of the starch of the flour into alcohol and carbonic acid gas, which, rising in bubbles, makes the bread light. A sudden chill prevents their growth, and the bread is heavy. Some germs are necessary to cause milk to become sour. Flies are great scavengers, eating from the walls germs that might cause sickness.

They are not at all particular about their food, and the day often comes when the fly dines upon one germ too many. It grows and multiplies rapidly, and before the day is over it completely fills the fly and sends out little sticky threads, which fasten it to the wall or window. You may often see them in wet weather. Upon these threads little bodies — spores — are borne, which blow about to tempt other unwary flies. Some serve locusts and grasshoppers in a similar manner. It would be a good way of getting rid of these

3- fly killed by mould, (hrom Thome and fiennett’s otructural and Physiological JDOtany. )

plagues were it not that, for these spores to multiply rapidly, moisture is necessary, and the locusts are not particular to time their visits to our gardens during the wet seasons.

Lichens grow on rocks, where they look like splashes of paint in many shades of red and brown, grey and green. They, too, have their place in the plant-world, and do their share of the world’s work. For ages they had been performing

their part long before flowers made the world beautiful. Small as they are, they can dissolve and absorb small portions of the rocks on which they dwell.

Gradually these plants crumble to dust, which may be used to nourish some less humble plant.

Mushrooms “ that spring up in a night” bear their fruit and die. Contrasted with these small short-lived plants are those that grow to immelise size and live through generations. We owe the oaks and the fir trees that beautify the western part of the Colony to the earliest European settlers, to whose unselfish foresight they stand as lasting monuments. The historical oak of French Hoek has blossomed and shed its fruit for two hundred years, but no date in history records the planting of the famous “Wonderboem” of Pretoria. As its branches have spread out they have sent down their stem-like roots, which support the branches like columns.

The life histories of the moulds, yeasts, and disease germs have been learned only in recent years, since microscopes have been improved ; but the old Hebrew poets, who watched the paths of the stars as they tended their flocks, studied the trees and flowers ; and we know our Saviour cared for them, for He often spoke of them in teaching His beautiful lessons. We, too, may study them without books and without knowing their long Latin names, though these have their uses. How unfortunate it would be if Johannesburgh or Springfontein had no names when we wished to book our luggage for those places. The long names of plants are not so formidable either, when stripped of their Latin endings. Thus deprived, Macowani reveals our friend-in-need. Dr. MacOwan, and how better could South Africa’s authority on orchids be honoured than by

Fig. 4. — Graphis elegans, a pictorial Lichen (natural size). (From Thome and Bennett’s “ Structural and Physiological Botany.”)

Plmit Life

naming a new Disperis, Bohisiana ? The paired leaf of Bauhima reminds us of the twins, Bauhin, who long ago devoted themselves to Botany. When we have found the two forms of fruit on one head of flowers, Diinorphothcca (twoformed capsule) seems a most appropriate name, and once having seen the little crown of pappus hidden among the long

hairs of the ovary, we shall never forget Cryptoste?nvia, which means hidden crown. If you have not studied Latin or Greek, ask help from your brothers and sisters who are in college. To speak of plants and their parts, we must have names, and no name in this book will be longer than Hermanuspetrusfontein.

Chapter II

Besides maintaining its own life, a plant’s activity is directed toward reproducing its like in the lives of others. One of the most usual means of reproduction with which we are familiar is the seed. Seeds may be very small, like those of orchids, heaths, or Streptocarpus^ or large, like the acorn and cocoanut. In each seed there is a tiny plant, the embryo. Before the parent plant sends her offspring out into the world to fend for themselves, the seeds are well provided with a nicely fitting coat and a generous supply of food, to serve them until they are able to make their own. The pine seed is provided with one thick hard coat, but most seeds have two, which fit so closely that when the seeds shed their coats the two come off together.

When seeds are put into the soil and watered, the coats begin to swell, if there is warmth enough. In the bean they become wrinkled. As the water soaks in farther the rest of the seed swells and fills the coat until it bursts, and the embryo begins to make its way out. The seed is said to germinate. This shows that the seed which was so hard and dry is alive. It was alive all the time, but did not grow.

What made it begin to show life ?

One of the simplest seeds to understand is the bean. It is an old and useful friend. In order to make out the different parts of seeds, it is- well to compare them with some which have just begun germinating, for then the parts separate more easily. For this purpose seeds may be put into a box of clean sand. A biscuit-tin is good, but care should be taken first to make holes in the bottom to insure drainage.

Plant broad and narrow beans, Indian corn, water-melon or pumpkin seeds, and any others which you may have gathered.

As soon as the bean plant begins to make its appearance above the soil, an examination will reveal two thick leaves placed opposite to one another. Between them there is a small leaf-bud with one leaf folded within another. They are attached to the stem, which extends below the first pair of fleshy leaves and joins the root. It may be difficult to say where the stem ends and the root begins. Now compare a seed which has been soaked in water a few hours. Before removing the seed-coat notice the scar or hilum by which the bean was attached to the pod.

At one end of the hilum is a small hole, the micropyle. The seed-coat comes off easily and the seed splits into two parts, which you will see correspond to the two fleshy leaves.

Fig. 6. — Bean seed before removing the coat.

Fig. 7. — Bean seed with coat removed.

Fig. 8. — Bean seed with one cotyledon removed.

They are called cotyledons. Between these two halves there lies a small curved body, at one end of which may be seen the two small leaves the plumule. The other end, which will make the root, is called the radicle. So a seed contains a whole plant, very small and compact, ready to develop into a large plant when warmth and moisture are supplied. The small plant folded away in the seed is called the Embryo.

Instructions for Work. — Make a drawing of the outside of a bean seed. Carefully look to see how the parts are placed within. At which end of the seed is the plumule with reference to the micropyle ? On which side of the seed ? Compare the arrangement of the narrow bean with that of the broad bean.

Make drawings of all that you see. Keep these drawings in a book which you will use for plants.

A loquat seed will separate into two parts, the cotyledons ; but the plumule and radicle cannot be so plainly seen.

Now make out the parts in the seeds of a pumpkin, water-melon, or calabas seed.

In all these seeds the little embryo has stored all the food which the mother plant provided, within the two plump cotyledons. But there are seeds in which the food is stored outside the embryo.

The pine seed shows this nicely. Remove the thick, hard seed-coat and cut the contents across. A ring of white food will be seen, the endosperm, surrounding a central part. If another is cut lengthwise, this central part will be recognized as the little pine tree, with the radicle pointing to the smaller end of the seed.

Instead of two cotyledons, several will be found. The plumule is too small to be seen.

When drawing a pine seed, draw the seed-coat around the endosperm. A thin papery bag will be found between the two. It once contained food. Draw it by a light line inside the seed-coat.

Fig. 9. — Seeds of Pinus Pi7ica in different stages of germination. I. Ripe seed in longitudinal section : s, testa ; e, endosperm ; w, radicle of embryo ; c, the cotyledons ; y, the micropyle end of seed, with the rootlet directed towards it. II. Germination commencing : , Testa ; s, ruptured, and rootlet ;

IV, protruding ; ?*, red membrane inside testa ; jr, ruptured embryo sac : B, portion of testa removed ; e, endosperm : C, longitudinal section ; c, cotyledons: D, transverse section.

III. Germination complete, the cotyledons, c, unfolding, and the hypocotyledonary part of stem, he, elongated, the main root, w, developing lateral rootlets, w'. (From Edmonds and Marloth’s '“Elementary Botany for South Africa.”)

In the Hottentot fig or T’gaukum (Meseml)ryanfhe?nim) the embryo is curved around the endosperm.

Examine some seeds of “mealies” or Indian corn {Zea niais). Notice a small raised place on one side toward the smaller end. By soaking the seed and removing the coat this

Fig. lo. — Seed of J)/eset)ibryanthcnium with curved embryo.

Fig. II. — Seed of Zea mats, a, embryo at one side of endosperm ; b, embryo rt moved ; c, seed cut through, showing plumule, radicle, and side roots.

little body may be removed. It is the embryo. The greater part of the seed is filled with endosperm. The embryo has but one cotyledon, which lies close to the endosperm on one

Fig. 12. — Hcemanihns a, embryo; b, endo-

sperm ; c, food outside the endosperm partly used ; u!', seed-coat.

side, and on the other is joined to the plumule and radicle. They are so covered by the folded cotyledon that only the tips can be seen.

The large seeds of the “April Fool” {IIcBma?ithns) have but one cotyledon. The embryo is a small rod-shaped body

Plants a7td theh‘ Ways in South Africa

Fig. 13. — Seed of “ Water Uintjes” (^Apo7iogeton). i, large fleshy cotyledon ; 2, plumule ; 3, small

radicle.

lying in the centre of the endosperm. Around the endosperm is more stored food (perisperm). It can be seen plainly, and will remind you of the empty bag in the pine seed.

Examine a date and compare the seed with that of Haemanthus.

“Water Uintjes ” {Aponogeto?i) has one large green cotyledon, a thin plumule, and a very small radicle. Its food is all stored in the cotyledon.

Plants which have two cotyledons are called Dicotyledons, those with only one are Monocotyledons. It is an important distinction. Most monocotyledons have endosperm. “Water Uintjes” (Aponogetou) is an exception. The plants in each group have other characters in common which we shall find out later.

In the HcEmanthus and date the embryos are so very small that the food supply seems unnecessarily generous ; but it takes a long while for the date to get a firm footing in the soil, and the “ April Fool ” is always liable to be overtaken by drought. Nature provides her children generously, and we all know, when it comes to a question of food, it is better to have too much than not enough.

By this time we have examined enough seeds to find evidence of foresight for the future of the little plants, and as we follow their life histories we shall find this wise provision all along.

How Seedlings behave when they

WAKE UP.

Mais comes up Head Foremost.

— You may mistake the little pointed object for a stem, but in a few days you will find it to be a hollow, pointed leaf containing another leaf rolled up within it. This pointed roll easily pushes up through the soil. After it is safely up, watch the outer leaf split open and the next leaf unroll.

The calabas seed has by this time backed out of bed. Here the stem grows faster than the leaves. It makes a loop above ground, and as it gradually lengthens it pulls out the leaves. A little thought will show that this is the better way for the calabas or pumpkin, as the leaves are not rolled, and would have hard work to push up through the soil.

Now pull up some of the pumpkin seeds to see what has been happening below.

The point at the lower end of the cotyledons has grown out to form a small root.

The seed-coat has split open, and there is a little peg where the root is coming out. Plants a day or two older will show that the arching stem is splitting the seed-coat, and that the peg is holding the lower edge firmly in the soil. How did the peg come to be just there ? There is nothing like it on the other side, where it would

Fig. i6. — The peg is spreading open the seed-coats.

Fig. 15.— The Calabas backs out of bed.

be of no use. What if the seed had been planted with the other side down ?

Let us find out by planting more, taking pains this time to plant them flat. The pointed end, toward which the radicle always points, is a little one-sided. The point is not quite in the centre, and the micropyle is beside it. We can place the seeds in one row with the point at the right, and those in another row with the point at the left.

The peg is an odd little body. It is made for a purpose, and grows only where it is needed. Sometimes the stem below the peg grows too rapidly, or the seed coat is not held firmly enough by the soil. Then the peg fails to hold the seed coat in place and the plant has to get out as best it can. Do such seedlings look as thrifty as others? In Fig. 17 the peg has done its work, and the coat has been left underground.

Why has the cotyledon of the mealie not made its appearance ? It remains down where the supply of food was stored, which it has been absorbing and passing on to the plumule and radicle. By the time these parts are able to make their peg has done its work dicle ; sr, first side Fig. 19. — Germinating bean seeds, for the little calabas shoots growing from n and b with one cotyledon plant. stem. removed.

own food the seed will feel quite soft. If you cut a seed through the centre from front to back, and look at it with a hand lens, you can see the little channels through which the food passes. The radicle was protected in the seed by a little pocket, as was the leaf. The cap does not grow as much as the leaf-cap does, and the radicle soon pushes through it.

In the Indian corn the first side roots come from the stem just above the cotyledon. They are a part of the embryo. In the pumpkin they come from the radicle which forms the tap root; they are not formed until after the root begins to grow.

Compare the germination of a common bean and that of a broad bean. Both come up with a loop. Does the same part of the stem form the loop ? How do the cotyledons behave in the narrow bean and in the broad bean ? The cotyledons do not grow as in the calabas or pumpkin. Notice how they wither as the food they contain is given up to the growing parts. When the loop pulled up the cotyledons in the narrow bean, the tender leaves of the plumule folded between them were also safely brought up. How is the plumule brought above ground in the narrow bean ? The plumule grows out into two pretty leaves. Notice carefully the little cushions near the lower end of their stems. Were these found in the calabas seeds ?

“April Fool” seeds {Hcemanthus) may not wait to be planted. The juicy berries within which they grow supply moisture, and when the right time comes they germinate of themselves. As growth begins the root is pushed out by the cotyledon, the tip of which, remaining in the seed, absorbs the stored food until the root is old enough to reach the soil and do its work. After a few days the plumule thrusts up its head through a slit in the base of the cotyledon. Does the tip of the cotyledon come above the soil ?

While studying the germination of April Fool seeds, compare them with germinating seeds of onion and date. The

Fig. 21. — Little “April Fool” plants ( H aetnanthns')

Fig. 22. — Growing seed of Aponogeton (“ Water Uintjes latter germinate very slowly. Plant them early in the year. A place may be left in the notebook for them.

Watch for acorns that have been left on the ground for several weeks after falling. Notice how the plant splits the hard shell, and how the root pushes down and anchors the seed.

Plant other seeds that are about your home. The Silver Tree has large seeds which germinate readily. Arum “lily” seeds may be compared with those of Hasmanthus. Aponogeton seeds may be found soon after flowering. Notice how little the radicle develops. A stem soon appears at one side of the cotyledon which bears roots below and leaves above.

Kafir corn may be germinated with Indian corn. In

Set'i/s and their Germination studying germination, take plenty of time to make simple drawings of each plant. Drawings should be made to show the plumule unfolded.

In the seeds we have studied the cotyledons have their special work to do.

The cotyledons of the broad bean simply yield up their food to the growing plant.

In Zca inais the cotyledon not only gives up its own store, but absorbs and passes on the food in the endosperm.

A third form is found in the date seed, where only the tip of the cotyledon remains within the seed to absorb the food, while the lower part pushes the radicle down into the soil, where it is safe from drying up.

The onion does nearly the same as the date. The cotyledon {a) absorbs the endosperm, {b) places the radicle, {c) comes up with a loop and brings the delicate plumule safely above the soil, {d) finally escapes altogether, becomes green, and behaves like a foliage leaf.

The pine and castor-oil seeds have a different habit. Instead of remaining within the seed-coat where the food is stored, they pull themselves out, bringing the food with them as little caps, which they consume on the way up, and gradually become good-sized foliage leaves.

Black wattles and the narrow bean cotyledons come above the ground to yield up their food, then wither and fall off.

The gourd family keeps the cotyledons, which grow and become green.

Here are seven ways, and you may find others. If you live in the East or near a botanic garden, you should study the seeds of Encephalartos (Kafir bread tree). Which type does it resemble ?

We have found that cotyledons (i) store food, (2) absorb and pass on food from the endosperm, (3) surround and protect the radicle and plumule, (4) bring them into position, (5) act as foliage leaves.

In no case have the cotyledons looked like the next leaves. Have you found any more showy than the next leaves ?

In order to watch the growth without injuring the seedlings.

seeds may be planted in a frame having glass sides. Ask the tinsmith to cut two pieces of galvanized iron the shape of Fig. 23. Bend them along the dotted lines. Nail the piece a-b to a board for support, and slip in on either side a piece of glass. Discarded photographic plates are just the thing.

Fig. 23. — Diagram for ends of glass germinator.

Fig. 24. — Seedlings showing root hairs.

Fig. 25. — Seedlings marked to show the place of greatest growth.

We will call this the Glass Germinator. Fill with moist sand. Thin cloth may be placed between the sand and the glass.

Place the seeds in different positions. Notice how quickly the roots will turn down and the stems bend upward. The work of the roots is to be done down in the soil, and that of the stems up in the light ; so the sooner they get into their proper positions the better.

Fine white hairs may be seen on the root and its branches to within a short distance from the tip. As the root pushes on, the oldest ones are worn off, but new ones are constantly formed toward the tip. They make their way in between the fine particles of soil in search of water.

Fasten some seeds, which have germinated until the roots are about an inch long, to strips of wood. Place them in an inverted flower-pot, in which the water stands to a height of two inches. Let the roots in one dip into the water * place the second lot higher, taking care that they are some distance above the water. After they have grown an inch or two, note the absence of root hairs in one lot of roots. If there is an abundant supply of water, there will be no need to provide special growths to obtain it.