DICOTYLEDONS 203 



determined only in the aeons to come. The botanist 

 can to some extent scan the progress of the past, and, 

 in a general way, trace a steady advance, involving 

 untold ages, from a simple Alga to the highly specialized 

 Daisy; but he knows not what the future has in store, 

 nor, as a strict scientist, dare he venture to assume the 

 role of prophet. 



The Dicotyledons have tried their mettle and demon- 

 strated their fitness to exist by their great success in 

 the struggle for existence. As a rule they give a pre- 

 vailing character to the vegetation of a district. In 

 certain situations, such as those occupied by Grasses, 

 Monocotyledons seem to dominate, and they unques- 

 tionably play an important and necessary part in the 

 economy of Nature; but in point of numbers they are 

 fewer than their more successful competitors, which 

 outnumber them by at least four to one. There are some- 

 where about 20,000 species of Monocotyledons distri- 

 buted over the world, whereas more than 80,000 species 

 of Dicotyledons have been distinguished. Few Mono- 

 cotyledons attain the dimensions of trees; but, setting 

 aside the Conifers, which, as we have seen, are Gymno- 

 sperms, in all temperate regions the forest trees are all 

 Dicotyledons. Among " weeds," the most successful 

 aggressors, in number of species, are Dicotyledons ; with 

 the exception of Grasses, there is barely a Monocotyle- 

 donous weed that is of any account. Angiosperms 

 generally have displayed remarkable elasticity in adap- 

 tation to environment, but it may be claimed that 

 among them the elasticity of the Dicotyledons is the 

 more pronounced. 



The plan of this book, as well as the limitations both 



