^fJQ PJ.AXT STUDIES 



j)li3'tes, the plants of the middle region. It is evident that 

 niesophytes gradually pass into hydrophytes on the one 

 side, and into xerophytes on the other ; hut it is also evi- 

 dent that nresophyte societies have the greatest range of 

 water supply, extending from a large amount of water to 

 a very small amount. 



It should 1)0 understood that tliese tlire(^ groups of socie- 

 ties, which are distinguished from one another by the amount 

 of the water supply, are artificial groups rather than natural 

 ones, for they hring together unrelated societies, and often 

 separate those that are closely related. For example, a 

 .swampy meadow is put among hydrophyte societies by tliis 

 classification ; and it may shade into an ordinary meadow, 

 which belongs among the mesopliytes. Proliably the largest 

 fact which may be used in grouping plant societies is that 

 certain societies are so situated that they seek for the most 

 part to rediice transpiration, and that others are so situated 

 that they seek for the most part to iiu'.rease transpiration. 



Ilowevei-. the factors which determine societies are so 

 numerous that they cannot lie presented in an elementary 

 Ijook, and the simjiler artificial grou])ing given above will 

 .serve to introduce the societies to observation. 



Upon a different basis another great group of societies 

 has been suggested as follows : 



(4) JIiiJoj)Jn//es. — The word means '•' salt plants. "" The 

 basis of classilication here dcjiends not si.i much ujion the 

 water supply a.s upon the fact that the \vater contains 

 certain salts which make it im]i(.issibl(! foi' most jilants to 

 live. Su<;li societies may be found ju'ur the sea-coast, 

 around salt sjirings, on alkaline Hats, oi' whei-ever the soil 

 contains these characteristic salts. 



