53. 



for it Is quite possible that in some "barks the water 

 might never have reached into the interior of the 

 sample, while in others the water undoubtedly penetiated 

 far into the interior.But it was impossible to cT3cure 

 definite blocks of bark which could be measured in 

 three dimensions and their swelling or shrinking areas 

 determined, for that reason the gravimetric method 

 was used which although not very accurate presents, 

 nevertheless, an explanation sufficiently plausible and 

 which seems to coincide with the explanation derive! 

 from the field observations," 



D.DISGUSSION 



From the study of the distribution of the 

 epiphytic polypody, it may be stated that the fern 

 begins its life on the tree in either of two v/ays. 

 It may start from spores blown into the crevices 

 of the ba: k or on a mass of mosses on the tree trunk. 

 These spores if they find sufficient moisture germinate 

 and develop prothallia which later produce young 

 sporophytes.Such stages of development of the fern 

 were found abundantly on the trunks of Juniperus 

 virginiana both in the autumn and in the spring. 

 The other mode of origin is that from the vegetative 

 fragments of the cporophyte which are v/ashed down from 

 higher branches to the lower ones by heavy rains. 



