2 BOTANY: PRINCIPLES AND PROBLEMS 



since he himself is a hving being, much of his speculation and 

 philosophy has naturally centered around problems which, in a 

 broad sense, are biological in their nature. The task of the 

 biologist in extending the field of our scientific knowledge of 

 plants and animals therefore assumes added significance from its 

 relation to some of the most profound questions with which man- 

 kind is confronted. As an integral part of the science of biology, 

 botany has already made notable contributions to our knowledge 

 of living things; and so long as man preserves that insatiable 

 curiosity toward Nature which has distinguished him as a think- 

 ing being, he will always in some measure be a student of plants. 



Aside from its theoretical interest, botany is also of ver}^ 

 great practical importance to mankind because plants touch 

 human activities so intimately and in so many ways. All food 

 which nourishes animals and man, and makes life possible, comes 

 originally from a union of water and a simple gas, carbon dioxide, 

 in the leaves of green plants. Our clothing, our fuel, our drugs 

 and countless other necessities of civilized life are likewise con- 

 tributed, directly or indirectly, by members of the plant kingdom. 

 As a means of quickening that intelligent appreciation of his 

 surroundings which should distinguish every educated man, a 

 scientific knowledge of plants is therefore of the utmost value. 



The Subdivisions of Botany. — Owing to the great mass of 

 diverse facts which it has accumulated and the many points of 

 view from which its problems have been attacked, every major 

 science has necessarily become divided into sub-sciences, each of 

 which makes its particular contribution to the whole. Thus 

 botany is composed of a series of specialized sciences. Three of 

 these — Systematic Botany, Plant Morphology and Plant Physi- 

 ology — are most worthy of note and are themselves subdivided 

 and recombined still further. 



Systematic Botany or Plant Taxonomy is concerned with the 

 names of plants and the classification of the vegetable kingdom. 

 Its object is to identify by name and description all the kinds 

 of plants which can be distinguished, and to arrange them, 

 according to their natural relationships, into those groups which 

 we call species, genera, families and orders. Since these relation- 

 ships can be determined only after a knowledge of evolutionary 

 history, the science of Plant Phytogeny, which endeavors to trace 

 the genealogy of the plant kingdom, is an important adjunct to 

 systematic botany. 



