The Angiosperms 169 



perfect expression, and these may be considered to 

 represent the highest achievement of the plant type. 

 Both in their superior numbers and adaptability 

 they show themselves to be, as a class, better fitted 

 to existing conditions than do any other class of 

 plants, and probably among them are the most recent 

 plant types that have been evolved. They include 

 plants adapted to practically all conditions of 

 life, and in one respect only are they surpassed by 

 the monocotyledons, namely in their adaptation to 

 a strictly aquatic condition. The number of truly 

 aquatic types is relatively small, although some of 

 them, like the bladder-weeds, are especially adapted 

 to aquatic life, and one peculiar group, the Podo- 

 stemonaceae, have been so modified as to look more 

 like algae than flowering plants. No forms are 

 known which live in sea water, the nearest approach 

 to this being certain salt-marsh plants, and the man- 

 groves. 



They may be considered, as a class, to be 

 more decidedly terrestrial in habit than are the 

 monocotyledons. From tiny herbs, living but a few 

 weeks, to giant trees, living as many centuries, di- 

 cotyledons are everywhere encountered, and usually 

 in greater numbers, both of individuals and species, 

 than are the monocotyledons. Except for certain 

 coniferous trees, the dicotyledons make up the for- 

 ests of temperate climates ; and with the exception 

 of the palms, they may be said also to constitute the 

 great bulk of the tropical forests. The tendency 



