423 



Miscellaneous. 



As it is an idea always kept in view, to write a series of lessons that will 

 enable the reader to use a " Flora," such as Trimen's Flora of Ceylon, an unusual 

 number of technical terms will have to be introduced into these lessons, but in 

 general there is no need to learn such terms ; for purposes of using the flora it will 

 suffice to know where to look for them. 



The reader should not confine himself to the pictures and the text ; he should 

 himself get all the plants, or parts of plants, mentioned, and dissect and draw 

 them ; too great stress cannot be laid on the advantages of drawing, for it enforces 

 attention to the important points, and ensures that the student shall see them 

 correctly. There is no need to be a trained draughtsman for this kind of work ; the 

 great thing is to draw to correct scale of relative sizes. 



Structure and Function.— There is reason to believe that the great number 

 and variety of plants now existing have arisen by a process of evolution or 

 gradual modification from a few simpler forms. How simple some forms of life 

 can be is only to be fully grasped by those who study them with a microscope. For 

 example, one of the common green moulds that grow upon trees is found to consist 

 of a vast number of single plants, each of which consists of a minute spherical 

 globule, which can absorb food through any part, can breathe through any part, 

 grows all over, and reproduces itself by simply dividing into two halves ; whereas in 

 the tea plant, for instance, water and food are absorbed by the root, worked 

 up in the leaves, carried about the plant by the stems ; reproduction is the business 

 of the flowers ; and so on. The great feature of the evolution that has gone on 

 has been the increasing complexity of the individual plant, as well as of the whole 

 vegetable kingdom. It is true that very many very simple plants now exist, but 

 the majority of plants are more or less complex. In place of simple, almost homo- 

 geneous organisms, any part of which may perform any function that may be 

 required, there now exist also a great many complex heterogenous organisms with 

 many different parts or organs performing different functions, a specialisation 

 which evidently tends to greater efficiency in the performance of those functions, 

 just as the division of the staff of a railway station into booking clerks, porters, 

 ticket collectors, signalmen, and others tends to greater efficiency than if any 

 man at the station were to do anything that was required. There is, in fact, in 

 plants a functional or physiological division of labour, accompanied by a structural 

 or morphological differentiation of organs. To investigate the functions of plants 

 is the province of physiology, and to do the same for the organs that of morphology, 

 which seeks to know and interpret the structure and development of all organs, to 

 trace and explain their origin, descent, and modifications, and to group them 

 according to their natural relationships by descent. 



We shall consider the different organs of the more complicated plants, and 

 deal with them in the order root, stem, leaf, flower, fruit and seed. 



THE ROOT. 



In an ordinary plant water is continually evaporating from the leaves, and 

 fresh water must be continually supplied from below, or the plant will flag. No 

 amount of rain falling on the leaves will make good the loss, for it is not taken 

 in by the leaves. It may be asked, why then do plants freshen up when there 

 is a shower of rain ? The reason is that the air being then saturated, no evapor- 

 ation can go on from the leaves, and consequently the water coming from the 

 root has nothing to do but to freshen up the leaves. 



The ordinary plant absorbs water from the soil, by means of the root. 

 This absorption of water, and of the various substances that are of course dissolved 

 in that water, is the chief object of the root. As there is only a limited amount 



