Botany for students of medicine and pharmacy;

Front matter

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Preface To First Edition

Tuis volume has been prepared to meet the need for an elementary treatment of Botany for the use of students of medicine and pharmacy. It is largely based on our Introduction to the Study of Plants and Introduction to the Structure and Reproduction of Plants, parts of which are reproduced in an almost unaltered form, since we feel that they present the matter in a manner equally suited to the needs of any student of the elements of the subject. In many places, however, the text has’ been specially modified to correspond with the requirements of the class of student for whom the book is intended, and for this reason a great deal of the matter dealt with in the works above quoted has been omitted.

We have embodied in this book the result of considerable experience in the teaching and examination of medical students, and of prolonged association with the Board of Examiners of the Pharmaceutical Society. The ordinary medical syllabus, and that of the Pharmaceutical Society’s Preliminary Scientific Examination is, we believe, adequately covered. The inclusion of a chapter on Bryophyta is due to a knowledge of this group being required in certain quarters, but we do not regard it as particularly instructive to the medical student. We have endeavoured, whilst meeting particular needs, to give an adequate account of the Vegetable Kingdom from the biological standpoint, and, in pursuance of this aim, have occasionally gone somewhat beyond the scope of any existing syllabus.

We are indebted to Dame Helen H. T. I. Gwynne-Vaughan for permission to reproduce Figs. 35-37, and to Prof. Bateson, F.R.S., and Miss Pellehew, for Fig. 157. A large proportion of the figures are original. Our acknowledgments are also due to Mr. E. Hatschek for revising the matter on pp. 69-72.

IDs Ihe Ise

LONDON, February 1921.

Preface To: Second Edition

THE present edition has been revised throughout and brought up to date. In particular the sections devoted to the physiology of plants have been considerably modified and in part rewritten. But there is no change in the scope or the manner of treatment. We are indebted to Dr. F. M. Haines for giving us the benefit of his experience on various matters relating to plant-physiology.

E, (ao

LonpDoN, June 1928.

vi

Introduction

DEAN GAISFORD once affirmed that there were three reasons why people should know Greek. “ In the first place,” he said, “it enables you to read the words of our Saviour in the original, in the second place it allows you to have a hearty contempt of those who are not acquainted with the language, and in the third place it leads to positions of emolument in the church.” Of his first reason it may justly be remarked that it is based on the strange assumption that Jesus talked in hellenistic Greek, of his second that it is hardly charitable, while of his third perhaps the less said the better. But forall that a littie reflection suggests that the professor-dean, in the pompous and rather priggishfashion proper in his day to his position, was dimly groping at the real defence of a study through which we have reached some of our highest spiritual and practical achievements since Erasmus. He saw that Greek enabled a man to make a better living out of the world and to have the broader hold on freedom which that allows; that it admitted him to an intellectual companionship which was an aristocracy by its possession of inward resources and inspirations that others had not got ; that it helped men to understand the Bible in the fullest way. I think this is what he meant ; he said it in blunter words.

Anyone can for himself parody any of the current versions of Gaisford’s remarks into a crude apologetic of the pursuit of any branch of knowledge which has technical applications to life as we live it—of, for example, the chemistry and physics and biology which occupy the earlier years of the medical curriculum. But the modern version—his quip is now nearly a hundred years old—is perhaps worth rather longer statement.

Taking the third and least important reason first, it is apparent vii

Viil INTRODUCTION that many of the sheer facts which are the data of the preliminary sciences are of direct and immediate use in practical medicine. The identification of sugar in the urine, the measurement of the pressure of blood in the arteries, the recognition of bacteria and moulds in infectious diseases are procedures of chemistry, physics and botany which are in daily use in practical medicine. An ability to understand these and a host of similar operationsmay not perhaps guarantee a position of emolument in the profession, but at any rate such a position is impossible without it. Then why not restrict the topics in these sciences with which the medical student is expected to familiarise himself to those which in this way have direct technical applications ? Botany, for example, ‘was at one time “ useful,” for it was an obviously necessary part of the training of the doctor that he should learn to recognise foxglove and deadly nightshade and monkshood when he had to collect his drugs himself. He now buys them from the druggist as digitalis, atropine and aconitine. Even now, however, a general knowledge of botany may be as directly useful to a doctor as a stethoscope. If he can distinguish the American poison vine from the common Ampelopsis he will from time to time be able to identify the cause and to achieve the cure of most distressing inflammations of the skin: if he can recognise a cruciferous plant he will know what to administer to a case of scurvy— a disease, due to errors of diet, which is cured particularly easily by plants belonging to that natural order. From the most purely utilitarian point of view, therefore, there are some things in botany that are worth knowing. And the reason why it is impossible to learn these and these only is simply that no one knows what is useful and what is not. Discovery is a process and not an event, and few things have been more striking in the progress of medicine in recent years than the way in which natural knowledge has come to be woven into its everyday work. The controlof malaria and yellow fever depends on our appreciation of how certain mosquitoes live and breed, the control of plague on the habits of fleas and rats, the adequate feeding of children on the nature of the food of cows and pigs. Modern civilisation, which we all believe to be modern progress, depends so much on the successful exploitation of the natural resources of the world that no one can tell what particular item of knowledge

INTRODUCTION iX is going to be useful—indeed, necessary—at any point in his pilgrimage. Any attempt therefore to learn what is at any one time of proved utility and to neglect everything else is bound to fail in its object: ten or twenty years of medical progress will make such changes in the list that the student who thinks himself well-equipped with practical knowledge will find as a middleaged doctor that he knows much that is useless and is ignorant of more that is useful. Utilitarianism is sure to be its own undoing.

There are fortunately broader grounds on which the earlier years of the curriculum can rest. Itis obviously a good thing for a medical man to have some knowledge of what the world is made of and how it works, because this information is an integral part of any satisfactory education. Everyone is the better for understanding the mechanism of the barometer whose indications he follows, for an acquaintance in a general way with the anatomy of the body and its way of working, for knowing something of the rare metals which go to make the nib of his fountain pen, for some idea of how a cabbage grows. A man who holds that the ups and downs of his weather-glass are vagaries of the devil, or that the cesophagus leads into the lungs, or that chalk is made of iron, can never be a fit member of a profession which requires more than most an imaginative and sympathetic understanding of the world and the people in it—requires, in short, an educated mind. One of the special qualifications which a training in the preliminary sciences is apt to give is whatis known as a “scientific ’’’ habit of mind. By this we simply mean the habit of drawing reasonable conclusions from premises of which one is reasonably sure, of adding two and two together so that they make four instead of five, of instinctively looking for the causes of effects and the effects of causes. It is by no means the prerogative of the natural sciences. The scientific method may be applied to irregular Greek verbs or to Roman history or any other matter of human interest just as much as to chemistry or physics or biology. Its more immediate association with the natural sciences is due to the fact that scientific subjects are generally susceptible to experimental inquiry while the humanities are not, and that it is by the experimental method that we have convinced ourselves that the “ scientific’? habit of mind gives us x . INTRODUCTION the best approximation we can make to the truth. An educated man must have the scientific habit of mind, and a doctor must be an educated man. He will not have a hearty contempt for his less fortunate brothers, but he will understand them better,

But a doctor ought to have a more ample acquaintance with these sciences than the educated man in the street. Medicine is a piece of applied biology and requires a generous training in the broad principles which summarise the relations of live things to one another and to inorganic nature. The interactions of animals with plants, and plants with one another, of all life to the dead background on which the real world moves, are immensely complex: to understand the life of a dandelion or an earthworm is difficult enough, but serious attention to what is known of these relatively simple cases is a necessary introduction to any attempt to understand how man lives and moves and has his being in a world which he has made more and more complicated for himself by progressively trying to wriggle out of the rules of nature. Any medicine which does not live in a biological atmosphere must be a maimed business, and the medical student cannot saturate himself too fully with the notions of biology. The mouth contains an assemblage of minute animals and plants which live in community with one another and with the man who furnishes a warm wet habitat for them; the large intestine provides different conditions and has quite another series of species; the dry exposed skin on the surface of the body has another. The harmonious relations of these bacteria and protozoa with one another and with their host are lable to go awry and any of the parties concerned may come to some damage. This is a special case of the general problem which botanists call cecology, and why different societies of bacteria live in the mouth, the rectum and the skin is just the same question as why different associations of higher plants give their characteristic appearances to oak woods, moors and marshes. To understand either question one must consider both. In some instances biology will explain medicine, in other cases medicine will illuminate biology. One of the most moving axioms of biology is that the world is an harmonious whole: no live thing—and no part of a live thing—lives for and by itself, and if the routine of its being is varied it will

INTRODUCTION xl still achieve, or at least attempt, the maintenance of this harmony. Correlation, adaptation and compensation are seen easily enough when we look at the world, but the experiments which convince us that this interpretation of nature is the right one are to be found especially in the field of medicine. In the presence of any disease or injury a live thing will do its part to put itself right again: a cut finger heals if it is left alone, a pencil does not sharpen itself. The business of practical medicine is to make people feel better, and it does this by helping on the natural processes of repair and restoration which are common to man and the earthworm: the mending of a broken leg depends on what the body does, the mending of a broken bicycle on what the engineer does. If anyone wants to play a good doctor’s part in the running of this wonderful pageant, he ought to know biology, he wants to read his patientsin the original. Besides, it makes medicine so much more amusing.

o»

GHAPTEF.

tls II.

LT IV. iV VI.

VIL.

VIII.

CONGR Nees

INTRODUCTION : 2 A ;

THE PLANT CONSIDERED AS A WHOLE

PLANT-HABIT AND DURATION ; 3 SEEDS AND SEEDLINGS 5 ; ; THE ROOT AND ITS FUNCTIONS . :

THE SHOOT A . : 2 :

THE STRUCTURE AND PHYSIOLOGY OF THE PLANT-

CELI=n, - : : ° GROWING POINTS AND CELL-DIVISION .

THE DIFFERENTIATION OF PLANT-CELLS Tur NON-LIVING CONTENTS OF CELLS BY-PRODUCTS AND SECRETORY ORGANS THE STRUCTURE OF Roors -

THE STRUCTURE OF THE YOUNG STEM THE EPIDERMIS . 5 , ; THE STRUCTURE OF THE LEAF . ‘

SECONDARY THICKENING , .

Xiiil

I4I xiV

CHAPTER

VL

XVII.

XXIT.

XXITI

XXIV.

XXV.

| XXVI.

AXVIT.

XXVIII.

XXX.

XXX.

Contents

THE PLANT IN RELATION TO ETS WATERe SUPPLY .

THE NUTRITIVE PROCESS OF THE PLANT : FOOD-STORAGE—ENZYMES

THE BREATHING PROCESS OF THE PLANT THE GROWTH OF THE PLANT PLANT-MOVEMENTS - THE ALG&.