DEPARTMENTS OF BOTANY 9 



edge of the structure of plants, just as an account of the 

 different kinds of steam-engines (e. g., locomotives, including 

 freight-engines, passenger-engines, switching-engines, etc.; 

 stationary engines, including horizontal engines, pumping- 

 engines, hoisting-engines, and so on) would be a description 

 of the form and position of the different parts of their ma- 

 chinery. Moreover, not until we know about the different 

 parts of a plant, as of a machine, are we in position to under- 

 stand well what each part is for, and how they all work to- 

 gether. A knowledge of plant structure has thus a twofold 

 importance. Similarly a knowledge of the materials which 

 enter into the various parts of a plant, as of a machine, is 

 necessary if we would understand its capabilities and use- 

 fulness. 



So one question leads to another, the proper appreciation 

 of one aspect of plants requiring also the study of other 

 aspects. In this way have arisen the different departments 

 of botany, each one representing a special point of view and 

 all being necessary to a comprehensive understanding of the 

 subject. 



To the various departments have been given special names 

 of which the following are the most important for a beginner 

 to remember: — 



Economic Botany views jjlants in their relation to man's 

 welfare. It is concerned with all the kinds which man uses 

 for food, medicine, clothing, shelter, ornament, or for other 

 purposes ; and all which are harmful to him as weeds, poisons, 

 or pests. The ways in which these plants are useful or harm- 

 ful, and to w4iat extent, to what peoples, for how long, and 

 why — such questions as these it seeks to answer as far as 

 possible. 



Chemical Botany is the study of the properties and quanti- 

 ties of the various substances found in plants. Since the 

 value of a useful plant often depends upon the presence of 

 some special substance, such as sugar, the economic botanist 

 has frequent occasion to learn aljout the chemistry of the 

 ])lants with which he deals. Such knowledge is also necessary 

 to an understanding of the life-processes of plants. 



Systematic Botany is concerned with the accurate descrip- 



