CH. IX] THE CLASSIFICATION OF PLANTS 395 



the color, or some members of one group may even adopt the 

 color of another. Hence all such single-feature categories 

 must be used in the knowledge of the ever-present possi- 

 bility of exceptions. 



The classification of plants is interlocked among the lower 

 forms with that of animals. The higher plants and animals 

 are, of course, perfectly distinct, their differences, in the last 

 analysis, centering in their different methods of acquiring 

 their food. Plants are typically organisms, or the descend- 

 ants of organisms, able to synthesize their own food from 

 inorganic materials by aid of sunlight applied through chloro- 

 phyll, this method permitting a sedentary habit, a con- 

 tinuous cellulose and lignified skeleton, and a sensitivity 

 confined to reflex action (page 55). Animals are typically 

 organisms unable to synthesize inorganic materials into 

 food, which accordingly they take from other organisms, by 

 methods involving active locomotion, a muscular system 

 with jointed skeleton, special sense organs, and ultimately, 

 in higher forms, the development of consciousness. Among 

 the lower forms in both kingdoms, however, these and all 

 other distinctions fail, for there are groups which include 

 both undoubted plants and undoubted animals, as in case of 

 the Flagellates (page 410), while other groups consist of 

 organisms which unite in themselves both plant and animal 

 characteristics, as in case of the Myxomycetes (page 412). 

 The explanation, however, is obvious, and attested by many 

 lines of evidence, the two kingdoms have been evolved 

 from the same ultimate ancestors, of which the groups and 

 organisms above mentioned are the surviving representa- 

 tives. 



Such in brief is phylogenetic classification, which under- 

 lies the four following chapters. The second system, eco- 

 logical classification, which deals with the vegetation of the 

 earth as distinct from its flora, will be considered in the final 

 chapter. 



