Botany : specially written to meet the requirements of teachers' D, matriculation, public service entrance, intermediate and pharmacy A examinations

Front matter

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Preface

Recent changes of syllabus in Teachers’ D, Publie Service Entrance and similar examinations have made it impossible for candidates to sit for Botany and other science subjects without doing a considerable amount of practical work. ‘To supply directions for such work, and at the same time to cover fully the whole Botany course prescribed for each of the above examinations, are the main objects of this book. English textbooks, designed to meet English needs, and dealing almost exclusively with English plants, are unsuited to the requirements of New Zealand students; while such New Zealand textbooks as deal with the subject treat almost exclusively of Morphology and Classification, and thus leave practically untouched the important branches of Ecology and Physiology, so that the student is left without guidance in such matters as the ‘Struggle for Existence,’’ ‘‘ Adaptation to Surroundings, ’’ ‘Plant Societies,’’ ‘‘Germination,’’ and ‘‘Nutrition.’’ There are, of course, admirable works, like those of Dr. Cockayne, which deal with one or more branches of New Zealand Botany; but these are not written nor are they intended for school purposes. The author, therefore, believes that by bringing together and correlating these different matters his book will supply a real want.

In selecting plant types, care has been taken to exclude those that are difficult of access; while, in the matter of experiments, only those have been described, which, after frequent repetition, have been found capable of producing obvious results without the use of elaborate apparatus or the need for specially skilful manipulation.

The student should realize at the outset that Botany is pre-eminently a subject demanding, in all its branches, personal investigation of things, not words. Merely to read the description of an experiment is a proceeding barren of useful result, but to carry it out with one’s own hands, and thus directly to verify or discover, is to open a door of knowledge that can never again be shut.

4 PREFACE

In any satisfactory Botany course field-work is of the first importance; for it is by the study of plants when growing under natural conditions that the student acquires a living interest, and at the same time obtains that broad and comprehensive view, which alone can illuminate the investigation of detail that must be carried out in the laboratory. In short, field-work vitalizes the whole subject.

In conclusion, the writer wishes to thank all those who have been so ready to give assistance—Dr. Cockayne and Mr. Laneaster for useful photographs and suggestions, and Mr. Ash, Chief Art Instructor of the Seddon Memorial Technical College, for his invaluable help in connection with the illustrations.

DEFINITION OF BOTANY IN PUBLIC EXAMINATIONS.

SYLLABUS FOR TEACHERS’ D CERTIFICATE.

The candidate will be required to show that he has acquired his knowledge of the following topics by observation, investigation and experiment:—

_The organs of flowering plants, their arrangement and principal modifications; their functions, so far as they can be ascertained by observation and simple experiments.

The general structure, distribution and arrangement of plant-tissues, so far as they can be studied with the aid of a good hand lens. The structure of fruits; the various kinds of fruits.

The main phenomena of the life-history (excluding microscopic processes) of common flowering plants; germination; establishment and growth; comparison of the different types of germination; the mechanism of pollination; fruit and seed dispersal.

Structure of garden soil; different types of soil and their air and water contents; rough methods of mechanical analysis of soils.

Elementary knowledge of the chemical constituents of plants and the sources from which the plant obtains them.

Simple qualitative and quantitative experiments illustrating the nutrition of plants, the conduction of water and food substances in the plant, storage of reserve material, respiration, transpiration, irritability.

The struggle for existence; adaptation of plants to their surroundings and to cold and drought, protection against animals; comparison of creeping plants, rosette-forming plants, shrubs, trees, and climbing-plants; the shapes of leaves and the causes to which they are due; plant societies.

The identification of common trees at different seasons by means of various parts and organs, such as buds, bark, leaves, ete.

6 DEFINITION OF BOTANY IN PUBLIC EXAMINATIONS

The. description and dissection of commonly occurring flowering plants (technical descriptions will not be demanded).

A general knowledge of the following natural orders:— Liliaceew, Ranunculacer, Crucifere, Umbellifera, Leguminose, Myrtacex, Rosacex, Composite, Gramines—with a special knowledge of at least one indigenous and one exotic typical member of each order.

The candidate will be required to forward, before the date of examination, a certificate in the prescribed form that he has carried out satisfactorily a course of praétical work based on the above syllabus.

PUBLIC SERVICE ENTRANCE.

This syllabus is practically the same as the above, the only real difference being the omission of the section relating to soils. The omission of ‘‘The Struggle for Existence,’’ ‘‘Trritability,’’ ‘‘Shapes of Leaves,’’ and the specified Natural Orders is apparent rather than real, for a study of these topics is necessarily implied in that of the other items enumerated.

MATRICULATION.

For Matriculation, Botany forms only half a subject, being included under the heading of Natural Science. In Natural Science two papers are set:— (a) A very general paper dealing broadly with Physics and Chemistry. (b) Any one of the following:— i. Elementary Home Science. ii. Elementary Hygiene and Physiology. iii. Elementary Zoology. iv. Elementary Botany.

The Elementary Botany is practically the same as that for D Certificate, the only important omission being that of the section dealing with garden-soil.

PHARMACY A.

For this examination the syllabus is essentially the same as that for Public Service Entrance, except for the fact that no plant description is demanded.

DEFINITION OF BOTANY IN PUBLIC EXAMINATIONS 7

PRACTICAL WORK.

Teachers’ D.—The certificate, a form for which may be obtained from the Education Department, should show that the candidate has taken (1) a course extending over two or more years at a Secondary School, the Secondary Department of a District High School or a Technical High School, or (2) an approved course for teachers arranged by an Education Board. In either case, not less than forty hours must be devoted to individual practical work by the candidates themselves.

Public Service Entrance, Intermediate, etc.—The certificate should show a one year’s course at least, as provided at a Secondary School, or in the Secondary Department of a District High School, or in a Technical High School. Of this course not less than thirty hours must be devoted to individual practical work by the candidates themselves.

Matriculation.—Every candidate must forward to the Registrar of the University before the examination a certificate from the principal of his school that he has carried out satisfaetorily a course of practical work based on the syllabus, provided that a candidate who is unable to comply with this condition may, with the permission of the Chancellor, submit his notebook of practical work to the principal of some Secondary or Technical School approved by the Chancellor for the purpose.

Pharmacy A.—No certificate required.

Contents

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PAGE Chapter I—Organs of Flowering Plants ie ee re Vegetative Organs ee a ey eS Reproductive Organs .. ai a oh 20 Summary Ae 65 Ss Se eae Questions 4 a an a ee Dec Chapter II—The Seed and Germination "a Seth Preliminary we an “aM Seeds .. sie a Mee abe Ae oy Germination ie 12 (ez .. 39 Phenomena of Germination 7 s: .. 43 Escaping from the Cover < xe .. 45 Summary abe is na os .. 48 Questions we we ae ao .. 49 Chapter III.—The Root rer ve oe ry poe Tropisms ‘ i iw ‘DS Arrangement of "Tissues a8 fs rel lhe Types “of Roots ; a eee Chemical Constituents of Plants. 9 Bue 1 The Soil oe ye wt eed Nitrogen Absorption =A “es Fi eee, Water Cultures a e as .. 84 Summary ae .3 ch! es 5g OO Questions 5 i 2 A ah, i cease f, Chapter IV.—The Stem ne we rts Mora Arrangement of Tissues ms “s .. 40 Types of Stems at ae hp sr. 93 Buds... oo S. +f oe LOUD Roots and Stems. or + tt See LLO Reserve Materials = ae A ae LOW Summary rye ot ad ie 5: 6 AO?

Questions Ae, ah ret ns oi LD Chapter V.—The Leaf te git bs: Structure A 28 dG Photosynthesis SES Respiration ae .. 125 Comparison of Respiration and Photosynthesis wn Ee Transpiration es sg oe Ee keys Leaf Forms i ‘A a eel hs Foliage Leaves and Seed ‘Leaves Ae: .. 144 Summary aus ut -. 145 Questions ra . 147 8

Chapter II. The Seed And Germination

PRELIMINARY.

Before dealing with the seed itself it will be necessary to learn how to test certain substances it contains, and to identify two gases, one needed for germination, the other produced thereby.

Oxygen may be prepared by heating in a test tube about a quarter of a teaspoonful of chlorate of potash mixed with a very small quantity of black oxide of manganese. After sufficient heating, a glowing splinter of wood plunged into the tube will burst into flame. Taking it for granted that the substance given off is oxygen, we have discovered the following facts. ‘Oxygen is a colourless gas without taste or smell, and vigorously supports combustion. The fact that substances burn in ordinary air, though not so violently as In pure oxygen, would naturally lead us to suppose that the air is diluted oxygen. As a matter of fact, in five gallons of air we have about one gallon of oxygen, diluted with about four gallons of an inactive gas called nitrogen. Eight-ninths of the weight of water is also oxygen. Oxygen is a very active gas, combines readily with a great many substances, and, in the act of combination, gives off heat. This combining of oxygen with some other substance is called oxidation, and the substance with which it combines is said to be oxidised. Under certain circumstances, the oxidation may be very violent and produce, at a civen moment, much heat and light. In such cases we all it burning. When coal burns in a fire we have this fierce oxidation. The oxygen of the air combines with 27 the coal very rapidly and much heat and lhght are produced. On the other hand, when oxygen combines with iron to form rust, we have slow oxidation, and, though the total heat given off is considerable, it is produced so slowly that the iron never gets appreciably hotter. Nevertheless, if a coil of fine wire be heated red-hot at one end and held in a jar of oxygen, it will burn fiercely and produce much heat in a short time. The great function of oxygen in the living world is to oxidise things and set free heat and other forms of energy. Energy is the power to do work. All know the work that can be done by the burning or oxidation of coal. The heat given off may be used to warm a room, drive a locomotive, or to produce the electricity necessary for lighting or for driving a tram ear. Neither animals nor plants could exist without oxygen. Animals absorb it through their lungs and use it to oxidise the food they have taken through the mouth, and thus to set free the energy they need for the body work. Plants, as we shall see later, use oxygen for the same purpose.

Carbon is a solid substance found in every tissue that goes to make up plant*or animal. The diamond is pure carbon, while graphite, charcoal, coal, and coke are more or less impure forms of the same substance. The presence of carbon in any organic material may be indicated by heating it in a test tube, when the presence of carbon is shown by the charring of the substance. Thus milk, meat, wood, leaves, sugar, starch, and bone will all char when heated, for all contain carbon. In most plants, at least one-half the dry weight consists of carbon.

_ Carbon-dioxide is a gas which is usually prepared in the laboratory by pouring hydrochlorie acid on marble chips. If these materials are not available the student may, however, obtain the gas by pouring vinegar on washing-soda in a test tube. Effervescence takes place owing to the bubbles of carbon-dioxide given off.

Carbon-dioxide is a very heavy gas, and can be readily poured from one vessel into another. Before pouring the vinegar on the soda have ready another test-tube containing about an inch of lime-water. Without allowing any of the liquid to pass over the lip, pour the gas from the first test tube into the second. On shaking the tube the lime-water becomes milky, and this milkiness is the recognised sign that carbon-dioxide is present. Now blow through a glass tube into clear lime-water, which, by becoming milky shows that the breath is heavily charged with carbon-dioxide. Next pour some lime-water into a shallow dish and expose it to the air. A milky seum soon forms on the top, showing that the air contains a certain amount of the same gas.

Now pour some lime-water into a jar of air, or better still, of oxygen. The liquid does not become milky, for in the small quantity of air enclosed in the jar there is not enough earbon-dioxide to produce an appreciable result. Now lower into the jar a burning candle, and withdraw it, when, having used up almost all the oxygen, it is about to go out. Then shake up the lime-water: it will become milky, showing that the carbon of the candle has combined with the oxygen to form ecarbon-dioxide. In the same way the carbon-dioxide of the breath is formed by the oxidation of the carbon in the food. It will be shown that a similar process of oxidation, producing carbon-dioxide, goes on in the plant.

Iodine in the dissolved state is used as a test for Starch, and may be prepared as follows :—

Dissolve a few crystals of potassium iodide in water, (about 1 gram to 75 ¢.c. of water), and add to this iodine crystals till the liquid is a dark brown.

To show the test, make a little thin starch paste. A single drop of iodine added to this will give a blue colour. In testing substances for starch, the best. results are obtained by scraping the material very fine, boiling in a test tube with water, cooling by letting the tap run on the tube, and then adding the drop of iodine. The cooling is very important, for, when the material is above a certain temperature, the blue colour will not appear. Various substances, such as potato, parsnip, and seeds may be tested in this way.

Fehling’s Solution is a substance used to test for grape sugar, which is present in various parts of plants.

The following rough and ready method of preparing the Solution will serve all practical purposes :—

Add tartaric acid to bluestone (copper sulphate) dissolved in water, till the colour is slightly green, and then add caustic soda till the solution is dark blue.

To show the test, crush a piece of apple or banana, cover with water, add a drop of Fehling’s Solution and boil in a test tube; a yellow or orange red sediment is formed, showing the presence of grape sugar. The earbon of the sugar has taken away from the copper in the solution some of the oxygen that was united with it, and thus caused the change in colour from blue to yellow. In other words the higher oxide of copper has been reduced by the carbon of the sugar to a lower oxide, which, being insoluble, has been thrown down as a precipitate.

Carbohydrates are solid substances that consist of carbon combined with the elements of water or, since water is a compound of oxygen and hydrogen, carbohydrates may be said to be formed from carbon, _ oxygen, and hydrogen, the oxygen and hydrogen being in the same ‘proportion as they are found in water. The most important carbohydrates are sugar, starch, and cellulose.

Sugar differs from the other two in being soluble and in having more oxygen and hydrogen in its composition. Sugar, as we shall find later, is abundant in most fruits as well as in many roots and sueeulent stems. Starch is insoluble in water and is present in most seeds and underground stems. Cellulose forms the bulk of all wood, while good filter paper as well as cotton wool are pure cellulose. The simpler tests for this substance are not always reliable, but the following can usually be applied with success :—

Soak the material to be tested, say cotton wool or filter paper, in weak iodine solution and then place on it a drop of strong sulphurie acid. A blue colour appears, which almost immediately changes ‘to black. Where this blue colour shows itself we may be sure that cellulose is present, but where it is not seen we cannot be so sure that it is absent.

Oils, which, like carbohydrates, are composed of carbon, oxygen, and hydrogen, but in different proportions, are plentiful in many seeds. In seeds such as the castor bean the presence of oil may be shown by rubbing the broken surface of the seed on a piece of tissue paper. A transparent greasy mark shows that oil is there. Where not plentiful, the oil may be extracted by crushing and soaking a number of seeds in ether in a tightly corked test-tube. The ether dissolves out the oil: after allowing the tube to stand for some hours, pour off the ether without disturbing the sediment of crushed seed, and allow it to evaporate in a shallow dish. When the ether has disappeared drops of oil will remain.

Proteins are found in all plants. Carbohydrates and oils contain carbon, oxygen, and hydrogen. The same three substances are found in proteins, but in addition, the gas nitrogen, the mineral sulphur, and, as a rule, the element phosphorus enter into their composition. Proteins then, are the nitrogenous as BOTANY compounds of plants. Place a drop of strong nitric acid on the white of a hard boiled egg. The yellow colour which appears shows the presence of a protein, in this case albumen. Now wash flour in a piece of fine muslin, till nothing but an elastic substance remains. This is gluten, another protein, which responds to the same test.

The protoplasm or living substance of both plants and animals is in the nature of a protein. Protoplasm is found only in living things, and there is no life without it. Indeed it is the life substance.

SEEDS.

Have ready a number of seeds of different plants, some quite dry and others that have been soaked in water for twenty-four hours. Seeds of the broad bean, searlet runner, pumpkin, sunflower, castor oil, onion, maize, and barley will be suitable for the purpose.

Examine a dry bean seed (Figs. 11-12). Observe that it is kidney-shaped and that it is covered with a brown coat, the testa. Note the black sear, the hilum, which shows where the seed was attached to the wall of the pod by a little stalk or funicle. Now take a seed that has been soaked, and, after drying, squeeze it between the finger and thumb. A drop of water will appear near one end of the hilum. This indicates the position of the micropyle, a small opening, through which, before it could develop into a seed, the ovule received a tube bearing fertilizing material from the pollen grain, and through which passes the bulk of the water absorbed by the seed.

Now remove the brown coat or testa which protects the more delicate parts within. Carefully separate the two fleshy cotyledons which contain the store of food that is to support the infant plant. Test the bean cotyledons for starch and protein. Both are present, the protein being legumin, a substance of similar composition to the protein which forms the curd of milk. The legumin is so plentiful that a drop of nitric acid placed on the inner side of the cotyledon produces an intense yellow. Now examine the young plant that lies curved between the cotyledons. Observe that it is attached to both cotyledons at about its middle point. The portion above the point of attachment is the plumule or young stem, and, by examining this with a lens, the undeveloped leaves may be seen.

Immediately below the cotyledons is the hypocotyl, which in the broad bean never appreciably develops; but. which, in the searlet runner, pumpkin, and many other plants lengthens to such an extent as to lift the cotyledons well above the ground. In such eases the hypocotyl develops to form the lower part of the stem. Continuous with the hypocotyl, but showing no definite point of junction therewith, is the radicle, or young root. This points towards the micropyle, through which, under suitable conditions, it will, later on, emerge. |

The cotyledons, plumule, hypocotyl, and radicle collectively form the embryo bean plant.

The so-called sunflower seed (Figs. 16-18) is really a fruit, in which the seed is still covered by the original seed case which has been formed from the ovary wall. Take one of the soaked specimens and observe that the seed case may be split along the edge. If this is done carefully it will be seen that the enclosed seed is attached to the pointed end by a very short stalk. On removing the thin seed-coat, separate the two cotyledons and observe the small plumule and radicle situated at the extremity of the pointed end. The iodine test shows that starch is absent from the cotyledons, but the nitric acid and tissue paper tests show that proteins and oil are abundant.

The castor-oil seed (Figs. 13-15) differs considerably from both bean and sunflower. At the pointed end is a spongy mass the caruncle, which rapidly absorbs water. If the seed be placed in hot water a bubble of air will come out of the micropyle, indicating that it is in the region of the caruncle. The advantage of this is obvious. On removing the skin it would appear as if there were not two cotyledons as in the bean and sunflower. As a matter of fact, in the castor oil bean the cotyledons are two flat bodies lying inside the oily mass that forms the bulk of the seed. This oily mass is called endosperm, and, like the cotyledons, serves to support the young plant. Seeds with endosperm are called albuminous while those without are termed exalbuminous.

In most dicotyledons, i.e, plants that have two seed-leaves, the seeds are exalbuminous, while in all monocotyledons, 1.e., plants that have only one seedleaf, they are albuminous. Now, with a sharp knife slice the castor seed longitudinally through its flatter sides into two fairly equal parts. As shown in Fig. 14, the cut edges of the two flat cotyledons will be seen with the radicle extending downwards from the point of junction below, and the tiny plumule pointing upwards just above it. Now slice another seed through its rounded sides as shown in Fig. 15. The desired result may not be attained till after several attempts, but finally, even without a lens, it should be possible to see the veining of the exposed surface of the cotyledon. The radicle appears below, and, with great care and patience, it will be possible so to split a seed as to see the plumule as well.

The reserve food in the endosperm consists of oil and protein, and does not respond to the test for starch. The cotyledons show abundant protein as well as oil.

It may be mentioned in passing that the scarlet outgrowth forming the cup of the titoki seed is similar

SEEDS

' BACK SECTION

FIG.IQ___ MAIZE GRAIN___FIG2 to the caruncle of the castor bean, but, being much larger, is called an aril. © ;

The Maize grain (Figs. 19-21) is a fruit and not a seed; but it differs from the fruit of the sunfiower. Whereas, in the latter, the seed case is merely a loose covering which can be removed, in the former, this ease has coalesced with the coat of the seed, and formed a single envelope which is firmly united with the food materials within. If on the growing corn-cob the development of the maize grain is carefully watched from day to day, it will be noted that there is no shedding of a seed case, and that therefore the ovary wall must fuse with the seed-coat and form part of the grain itself. Externally the grain is a blunt wedgeshaped body flattened on one side and having a rough apex which shows its point of attachment to the cob, and in which is the opening that corresponds with the micropyle of a dicotyledon. This may be located by placing the grain in hot water, when a bubble of air comes out as in the case of the castor bean. On the flat side, is a more or less triangular depression bisected vertically by a narrow ridge which indicates the position of the radicle and plumule. Now take a well-soaked grain,and, with a pin, prick away, from the side remote from the depression, the endosperm, which above and on the outside consists of amber-coloured matter, and further in of white easily powdered substance. In this way a tough elastic shield-shaped body will be exposed. This is the cotyledon, attached to the front of which may be seen the plumule and radicle forming a straight line on the flat side. Now split another grain through the flattened sides as shown in Fig. 21. In this, with the assistance of a lens, the structure of the young shoot may be seen. The iodine test shows that the endosperm is chiefly starch. When a drop of nitric acid is applied to the eut surface of the grain, the cotyledon becomes yellow, showing the presence of protein, but the endosperm, except on its extreme outer edge, remains unchanged. Oil, though present, is not abundant. The foregoing investigations show that the true difference between monocotyle donous and dicotyledonous seeds is, as the names would suggest, that in the embryo of the former there is only one cotyledon, while in that of the latter there are two. Moreover, endosperm, which is present in all monocotyledons, is found in but few dicotyledons.

The Coconut is well worth study. It is really the kernel of the fruit, and, like a plum stone, consists of the seed contained in a hard shell. The white material that lines the shell and is eaten, is the endosperm, and the dark coat that adheres to it when it is broken away from the shell is really the seed coat. The germ is less than half an inch long, and is situated immediately beneath one of the three eyes, the substance of this eye being thin and soft, and on germination affording a means of exit for the plumule. In the hottest part of the summer, place a coconut in a box of sawdust and keep it in a warm place, watering it thoroughly from time to time with Iunkewarm water. At night, wrap the box in an old woollen rug. The seed will germinate and the plumule appear through the eye. Now break open the nut and note the huge sponge-like sucker that absorbs the milk and flesh to be conveyed in solution to the young seedling.

The Date stone is a seed in which the hard material is endosperm. The embryo plant lies at the back on the side opposite the groove a short distance below the middle. On cleaning a date seed a depression will be noted at the back, where by scraping with a knife, the embryo plant may be exposed. This hes in a small cavity, and the sprouting rootlet makes its way out through the thin covering at the depression. The whole embryo may be extracted by placing the edge of a pocket-knife in the groove, and giving the back of the blade a sharp tap. The seed splits and sets free the embryo. It is difficult, even with a lens, to distinguish cotyledon, radicle, and plumule. Soak the split endosperm in weak iodine solution. The fact that there is no blue coloration shows that starch is absent. Now place on the split surface a drop of strong sulphuric acid and the blue colour which indicates the presence of cellulose immediately appears.

Speaking broadly, we have now arrived at the conclusion that the seed is really a young plant which, together with its store of nourishment, has been formed from the ovule of the flower while still attached to and forming part of the parent plant. At a certain stage, the development of the embryo plant ceases, and we say that the seed is ripe. All growth then stops, and the seed, becoming dry, goes into a resting condition. This temporary arrest of development is an obvious advantage. The seed ean, to some extent, choose its own time for renewal of growth. If, in the autumn when most of the seeds fall from the parent plants, the embryo were still growing, it would mean that the young plant would have to establish itself under adverse conditions. Autumn, in many places, is the driest season of the year, and the tiny seedling would thus have to contend with scarcity of water, and later on be overwhelmed by the frosts and snows of winter. Instead, the embryo remains dormant till the warm spring rains supply the conditions most favourable to its growth.

The Mangrove, which grows on the mud-flats of the tidal inlets of the Auckland Peninsula, is modified to suit its peculiar environment. If the seed were dropped into the mud in an absolutely dormant state it would probably be carried out to sea before it had a chance to germinate. To avoid this, most mangroves show no arrest in the development of the embryo, growth being continuous from ovule to fully established tree.