few physiological details have also been mentioned, here and 

 there, in the other parts where this has been thought advisable. 



Classification aims at arranging all plants in groups accord- 

 ing to their resemblances, with the object of facilitating the 

 identification of plants and of enabling anyone to rapidly ac- 

 quire a knowledge of the plants of any particular region and of 

 their correct names, as universally recognised by botanists. 



Vegetable Pathology includes the study of plant diseases, 

 wounds and injuries. 



Geographical Botany considers the distribution of plants 

 over the earth and its causes. 



4. If we take a seedling of any of Principal 

 our common forest trees we can at once distinguish : anTt 



(a) The Root which goes downwards and firmly anchors 

 the plant in the substratum on which it is grow- 

 ing. 



(6) The Shoot which goes upwards in a direction dia- 

 metrically opposite to that of the root and which 

 consists of an axis, or stem, bearing green leaves. 



It will help us to understand the various forms assumed by 

 these two sets of organs and their behaviour under different 

 circumstances if we realise, at the outset, that the root ab- 

 sorbs from the substratum in which it is growing water with 

 mineral substances in solution, which, however, are as yet use- 

 less to the plant as food and which may be therefore called 

 raw food materials. This water ascends the stem and passes 

 into the green leaves. The protoplasm in these leaves, by the 

 aid of the green chlorophyll and when it is supplied with 

 water by the roots and has air and light in contact with it, is 

 able to build up a carbohydrate, which usually first becomes 

 visible in the form of starch, from the carbon dioxide of the 

 air. This starch contains the energy by means of which the 

 plant is able to live, grow and perform its vital functions is 

 able not only to feed and keep alive its protoplasm, but also to 

 actually manufacture additional living protoplasm from the 

 inorganic substances brought up by the roots and to carry out 

 other work. The root must thus grow and spread in the dark 

 and moist substratum, while the shoot must come forth into 

 the sunlight and air in order to obtain its supplies of carbon 

 dioxide and to expose its chlorophyll to the rays of sunlight. 



The shoot also eventually gives rise, first, to flowers and 

 then, to fruits, the latter containing the seeds which will once 



B2 



