15. 



curled up, as it always dLm- in dry weather, its roots 



"beneath the "bark were perfectly turgid and showed 



no apparent suffering from lack of moisture. This 



olDservation suggests at once that the character 



of the "bark is as important a factor in the distribution 



of the epiphyte as is the light, Even when the light 



conditions are favorable, a tree possessing a homy, 



a stony, or a flaky bark does not furnish the 



proper support for the polypody, since its roots 



can not penetrate into the stony or horny bark,while 



on a flai:y bark that sheds frequently, such as of 



the pine or the sycamore, the young epiphyte lias hardly 



time to develop strong anchoring roots when the bark 



is shed carrying with it the young plant to the ground. 



In most cases, however, the spore fails to germinate, 



for no prothallium has ever been found on either 



the pine or sycamore in the northeastern part of 



Mississippi. 



It seems possible that both light and the 

 character of the substratum might be responsible 

 for the diversity in the distribution of the epiphytic 

 fern as it appears from a field study of the seven 

 stations. To determine this definitely the writer 

 was le I to carry on quantitative physiological 

 and ecological experiments in two of the observed 

 stations for a definite period of time. It was thought 



