PLANT ECOLOGY 327 



made mesophytic. As contrasted with hydi-opliyte and xero- 

 phyte societies, the mesophyte societies are far richer in 

 leaf forms and in general luxuriance. The artificial soci- 

 eties which hare been formed under the influence of man, 

 through the introduction of weeds and culture plants, are 

 all mesophii-tic. 



Among the mesophyte grass and herb societies are the 

 "arctic and alpine carpets," so characteristic of high lati- 

 tudes 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 ; '• pasttires," drier and 

 more open than meadows. 



Among the woody mesopliyte societies are the ''thick- 

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

 pure or forming a jungle of mixed shrulis. brambles, and 

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

 regions, rich in forms ai\d foliage display, with annual faU 

 of leaves, and exhibiting the remarkable and conspicuous 

 phenomenon of autumnal coloration : ' • rainy tropical for- 

 ests." in the region of trade winds, heary 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 bottnd together in an inex- 

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

 luxuriant growth of numerous epiphytes. (^See Figs. "2S8, 

 289.) 



