50. 



"baxk of those trees which Ijore no epiphytes, showed 

 no marked difference in the acid content, In fact, 

 the acidity of the "bark ot* of the "humus" on the 

 bark appeared to vary with the moisture content 

 Hs^ of the air as v;ell as with the time of the 

 day, It was found that the acidity was slightly hi^er 

 early in the morning than it was at noon,ajnd during 

 a rain or immediately after, the. bark or the "humus" 

 also showed a slightly higher acidity than in dry 

 weather, It was found further that the bark of those 

 trees which never bore any epiphytes contained aja 

 acidity of the same concentration as the bark of those 



that bore an abundance of the epiphytic fern and 

 mosses, The teste also revealed tlat the fern occurs 

 not only on slightly acid^soil" but is frequently 

 found also on slightly alkaline "soil", It is true, 

 however, that on the bark of the pine which exhibited 

 an acidity of 4,5 (P„ -/allies) the fern never occurred. 

 There, it is believed, the real cause of the absence 

 of the epiphytes was not the high acid content of the 

 bark, but the physical character of the pine bark ( ginus 

 taeda and P,echinata),It thus appears from a study of the 

 chemicail reactions that acidity or alkalinity of the 

 substratum does not influence the occurrence ajid dist- 

 ribution of Polypodium polypodioides. 



