4 ELEMENTARY STUDIES IN BOTANY 



body of a plant develops, from the egg to the adult; and 

 still later to conclusions as to how plants develop from one 

 another, a subject which is called evolution. If the classifi- 

 cation of plants is likened to the recognition of the family 

 connections and the names of people, the study of the 

 structure of plants may be likened to the study of the struc- 

 ture of the human body and the details of its development 

 from the egg to the adult. 



A third subject of study is the work of plants. It must 

 be remembered that plants are living things that use food, 

 grow, and reproduce, and all this means the work of a liv- 

 ing body. The study of the structure of plants is like the 

 study of the parts of an engine and how they are put together, 

 but the study of the work of plants is like the study of the 

 engine in action. It is evident that a study of the structures 

 of plants finds its meaning in helping one to understand the 

 activities of plants, just as a study of the structure of the 

 human body finds its motive in helping one to understand 

 the human body alive and doing its work. 



A fourth subject of study is the diseases of plants, which 

 often ravage our crops. The chief causes of these diseases 

 are other plants, so that this study involves a knowledge 

 of the structure of two sets of plants, those that attack and 

 those that are attacked. In addition to this, it involves 

 a knowledge of two kinds of work, the work of the plant 

 when in health and its work when diseased. The study 

 of plant diseases is regarded as a very practical one, but it 

 is evident that it cannot be carried on effectively without 

 a previous knowledge of the structure and work of plants. 

 Among the plants that induce disease in other plants are 

 the bacteria, which are also conspicuous in causing certain 

 diseases among human beings. These minute and peculiar 

 plants require such special treatment for their study that 

 they form a subject by themselves and demand a specially 

 trained group of botanists. 



