PLANT ECOLOGY 307 



made mesophytic. As contrasted with hydrophyte and 

 xerophyte associations, the mesophyte associations are far 

 richer in leaf forms and in general luxuriance. The arti- 

 ficial associations which have been formed under the influ- 

 ence of man, through the introduction of weeds and culture 

 plants, are all mesophytic. 



Among the mesophyte grass and herb associations are 

 the " arctic and alpine carpets," so characteristic of high 

 latitudes and altitudes where the conditions forbid trees, 

 shrubs, or even tall herbs ; " meadows," areas dominated by 

 grasses, the prairies being the greatest meadows, where 

 grasses and flowering herbs are richly displayed; "pas- 

 tures," drier and more open than meadows. 



Among the woody mesophyte associations are the "thick- 

 ets." composed of willow, alder, birch, hazel, etc., either 

 pure or forming a jungle of mixed shrubs, brambles, and 

 tall herbs : " deciduous forests," the glory of the temperate 

 regions, rich in forms and foliage display, with annual fall 

 of leaves, and exhibiting the remarkable and conspicuous 

 phenomenon of autumnal coloration; " rainy tropical for- 

 ests," in the region of trade winds, heavy rainfalls, and 

 great heat, where the world's vegetation reaches its climax, 

 and where in a saturated atmosphere gigantic jungles are 

 developed, composed of trees of various heights, shrubs of 

 all sizes, tall and low herbs, all bound together in an inex- 

 tricable tangle by great vines or lianas, and covered by a 

 luxuriant growth of numerous epiphytes. (See Figs. 288, 

 289.) 



