43. 



of the tree has a definite regional distribution in 

 both vertical and radial directions and this vertical 

 and radial distribution is infuenced primarily by the 

 evaporating power of the air, Thus, v;here the evapration 

 rate is the lowest the epiphytic flora consists of 

 hepatics (Fr ul^ia virp:inica ),of various mosses, and 

 of Polypodiu m polypodioides» As the evaporation rate 

 increases the hepatic begins to disappear leaving only 

 the mosses and the fern;v;ith the further increase 



of the evaporation the fern disappears and lichens come 

 in, In regions on the tree where the evaporation is 

 still greater, the mosses disappear leaving the lichens 

 as the sole epiphytes, Evidently the evaporating power 

 of the air plays a very important part in the dictributioa 

 of the epiphytes on a tree, When each of the other 

 conditions is presented graphically in the same manner 

 as the evaporation; ths,t is , starting with the lowest and 

 gradually going up to the maximum, then, when the 

 corresponding epiphytic flora for each station is 

 given, there appears to be no definite relation between 

 the distribution of any of the epiphytes and that of 

 the maximiHii effect of any one of the other factors, A 

 study of the graph of the light intensity (Fig, 15) 

 suggests that the hepatic occurs where the light is 

 the weakest, the mosses and the fern seem to endure 

 light of more or less moderate intenGity,v.hile the 



