22 INTRODUCTORY. PLANTS AND ANIMALS 



and whose time is strictly limited, is intended to empha- 

 sise this point of view. But such a student must under- 

 stand that if he is to acquire a foundation which shall 

 be of real use to him in his later work he must give 

 himself freely to the labour of acquiring a firm elemen- 

 tary knowledge of the nature and constitution of the 

 bodies of plants, of the outline of their structures and 

 of their various activities, not only from books and 

 lectures, but also at first-hand in the laboratory. 



What is a Plant ? Differences between Animals and 

 Plants. — The animals and plants with which we are 

 most familiar are the higher, i.e. the more complex 

 ones. They mostly live on the land, and are on the 

 whole, though by no means invariably, bigger than 

 the lower, less complex, forms. Certain outstanding 

 differences between the familiar higher animals, on 

 the one hand, and the familiar higher plants, on the 

 other, are very obvious. The animals move about, 

 the plants are rooted in one place : the animals are 

 compact, the plants are branching, in their habit of 

 body : the animals are variously coloured, the plants 

 are green, or at least have green leaves. The most 

 important functional difference is that animals consume 

 solid food, while plants do not ; and this is really the 

 root of all the other differences. 



The locomotion of animals is related to the fact 

 that they have to move about to find their food, which 

 must be organic, i.e. must consist of special complex 

 chemical substances forming part of, or produced by, 

 other animals or plants, while the food of plants consists 

 of liquid and gaseous inorganic substances which are 

 found everywhere in the earth and air. 



The compact form of animals is connected with the 

 necessity of locomotion and with the fact that the 



