16 THE EVOLUTION OF PLANTS 



Evolution is true, are related to each other in 

 the same way as the members of a human family, 

 though more distantly. Plants belonging to 

 the same natural family will at any rate be more 

 closely akin to each other than to members of 

 other families; the families belonging to the same 

 natural class will be more nearly related than those 

 of different classes, and so on. 



There are, however, great difficulties; we can- 

 not always be sure that our groups are natural, 

 and even if they are, we are still a long way from 

 being able to trace their descent. The compara- 

 tive method, applied to the study of the struc- 

 ture and life-histories of plants, has accomplished 

 a great deal. The great Hofmeister, sixty years 

 ago, established, once for all, the main lines of 

 relationship between the Flowering Plants and 

 the Higher Cryptogams (Ferns and their allies), 

 and to a certain extent, between the latter and 

 the Mosses; his work still forms the foundation 

 of all our knowledge of the affinities of these 

 great groups of plants. But, in questions of de- 

 scent, all work based on the comparison of living 

 forms leaves us in uncertainty, because the plants 

 we are comparing are all, so far as we know, of 

 equal antiquity; all belong as it were, to one 

 generation. The comparative work of Hof- 

 meister gave us very good reason for believing 

 that Conifers and their allies were descended 



