INTRODUCTION 3 



that every plant cares for two things : (1) the support of 

 its own body (nutrition), and (2) the production of other 

 plants like itself (reproduction). In the cultivation of 

 plants nothing is so important as to know about their nu- 

 trition and reproduction. Knowledge of the nutrition of 

 plants enables one to secure vigorous plant bodies, and 

 knowledge of the reproduction of plants enables one to 

 secure desirable races of plants. Most cultivators of plants 

 follow rules that they do not understand, but to learn such 

 rules without learning plants makes one an apprentice 

 rather than a student. 



5. Various aspects of plants. Plants are studied from 

 numerous points of view, so that botanists are divided into 

 many groups. The oldest subject of study was the classi- 

 fication of plants, which means discovering their relation- 

 ships, assigning them to natural groups, and giving them 

 names by which they may be recognized. In human society, 

 such a study would be the recognition of family relation- 

 ships, the grouping of people by families, and the use of 

 names to distinguish individuals. Just as individuals are 

 distinguished by two names, so two names are given to 

 ^ach kind of plant, and Quercus alba (white oak) is the name 

 of a plant, just as John Smith is the name of an individual. 

 Plants differ from human individuals, however, in that they 

 have no family records, so that botanists are compelled to 

 trust to certain resemblances to indicate the family connec- 

 tions. This means that plant classification must change as 

 the knowledge of resemblances and differences increases, so 

 that the work of classification demands continuous attention. 



A second subject of study is the structure of plants. At 

 first only such structures were included as could be seen 

 with the naked eye ; but with the invention and improve- 

 ment of the microscope, the minute structures came to be 

 studied also, so that it was possible to know how the body 

 of a plant is made. This led later to a study of how the 



