46. 



occurrence and distribution of P. iDolypodioides 



nor on the epiphytes associated with it .It is the 



sum total effect of the first three conditions 



on the evaporating power of the air in the immediate 



vicinity of each station on the tree whi ch is 



responsible for the definite epiphytic flora on the 



given station,' 



B, CHEMICAL ANALYSES 



Having determined the influence of the climatic 

 conditions on the distribution of Polvpodiiim 

 polypodioides the writer was confronted v/ith the 

 problem of the source of water supply and of mineral 

 nutrients needed by the epiphyte in its development 

 and growth, In order to determine whether the epiphyte 

 derives the necessary material from the substratum v/hich 

 it inhabits or from the dust of the air .chemical 

 analyses were made of the "humus" gathered from the 

 bark of the tree on which the epiphyte was growing. 

 An analysis was also made of the epiphyte itself. 

 To determine hov/ much of a contribution to the chemical 

 composition of the "humus"the bark itself made, the 

 bark of the trees that bore epiphytes was analyzed 

 and likewise the bark of those trees that did not bear 

 them, In connection with this work, the writer wishes 

 TO express his thanks to Dr,W*F,Hand, State Chemist 

 of Mississippi and his assistant Mr, H.Solomon for 



