27. 



these habitats to the sides of prostrate trunks 

 or fallen logs»"He found that the I^ymenophyllaceae 

 obtain most of their water through the absorbing 

 power of their leaves, though the roots also function 

 as water absorbing organs, The drought-resisting 

 species are capable of absorbing atmospheric humidity 

 when the leaves are placed in an environment of very 

 moist air especially if the surface of the leaves is 

 dry.Miehe (19) found that Polypodium vulgare was 

 confined to the branches of the oak.He also found 

 that Sorbus» Amelanchier. end Sambucue occurring 

 as "epiphytes" were not restiricted to any particular 

 side.Olsen (21) found that epiphytic bryophytes 

 are mo'^ commonly found on the upper side of inclined 

 trunks.This, he thinks, is due to the rain falling 

 vertically in the woods so that the upper side of 

 the inclined trunk gets the most moisture, The conditions 

 which affect the bryophytic vegetation, according to 

 Olsen, are the age of the tree, position in regard 

 to light, position in regard to wind,position in regard 

 to rainfa21,the species of the tree, and the chemical 

 composition of the "soil, Of these, the age of the tree 

 is the most important one since it affects the 

 character of the bark,Young trees possessing smooth 

 bark offer no footing for epiphytic grov/th.When the 

 tree becomes older fissures appear in the bark in 



