CHAPTER I. CLASSIFICATION OF PLANTS. 265 



both possible and of great importance to every intelligent 

 man. 



Classification and, Naming of Plants. All plants are more 

 or less nearly related to each other, not only in structure and 

 function, but without doubt also genetically or by descent. 



The forms that gladden the face of the earth to-day are the 

 descendants of the sombre vegetation of the far-off Carboniferous 

 Age, whose remains, in the form of coal, supply the civilized 

 man of the present with fuel to warm his dwelling and drive his 

 steam machinery; the coal plants, in turn, were descended 

 from the still more remote and simpler vegetation of the 

 Silurian seas. 



We shall best understand what plant classification means, the 

 relation of past to present forms, and of present forms to each 

 other, by means of a symbol — by picturing to our minds the 

 system of life as a great tree. This tree began its life in 

 the very remote past, in some very simple form, probably a 

 shapeless bit of living jelly. From this as a common trunk, 

 as time rolled on, branches diverged, which have continued 

 to develop and ramify, and spread wider and wider, until the 

 present time. Some branches, however, that throve for a 

 time, were overshadowed by others, and finally decayed and 

 died ; but there still remain innumerable twigs and small 

 branches of the wide-spreading top ; all else is buried in the 

 debris of the past, its outlines only being traceable in the 

 fossil forms which have been preserved to us. On examining 

 the living twigs that remain, we naturally find them distributed 

 into groups and clusters of various sizes. The members of a 

 cluster of twigs we may trace back to a common branch, those 

 of adjacent clusters similarly converge to other branches, and 

 these again converge to larger ones, and so on. It is the busi- 

 ness of the systematic botanist to move about among these twigs 

 and branches of the great tree of vegetable life, and discover 

 their real relationship to each other, to trace back the branches 

 as far as possible toward the common trunk. 



Thus botanical classification has for its object the discovery 

 of the natural or genetic relationship of plants. 



Looking about among the varied forms of vegetation, the 

 botanist finds plants that closely resemble each other in form, 



