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MOSSES RARE IN PHILADELPHIA 



George B. Kaiser 



The study of almost any locality will reveal peculiarities in the distribution 

 of moss species which furnish food for thought and conjecture concerning the 

 why and wherefore of their occurrence in given places, while in other places ap- 

 parently repeating exactly the same conditions of soil, moisture, and exposure, 

 they are altogether absent. 



For instance, in the city of Philadelphia, in clefts of granitic rock along the 

 Wissahickon Creek, there are several stations for Rhahdoweisia crispata (Dicks.) 

 Kindb. — long confused with Rhahdoweisia fiigax (Hedw.) B. & S. — an alpine, 

 subalpine, or mountain moss which is very rarely found in the lowlands. I have 

 searched the clefts of granitic rocks for miles about, but have discovered no other 

 growth of the same species. This moss does not fruit, but vegetatively subsists 

 in these few spots restricted to a limited area. 



On a northeasterly facing bank, also along Wissahickon Creek, for five years 

 Buxbaumia aphylla L. grew in a colony which increased from lo to 70 capsules, 

 then decreased, altogether disappearing after 1914. Its neighbors were Dicranella 

 heteromalla (Hedw.) Schimp., sparse Catharinaea angustata Brid., and immature 

 specimens of a species of Cladonia. Although almost numberless banks of a sim- 

 ilar nature have been carefully observed for years, I have found Buxbaumia else- 

 where only in one locality in Delaware County and in the Pocono Mountains 

 near Tobyhanna. How and why did the spores find these rare banks congenial 

 substrata? Webera sessilis (Schmid.) Lindb. — though of much more frequent 

 occurence — also seems to display a certain whimsicality in the banks it chooses, 

 leaving scores of similar banks bare of its presence. 



There are many rocky stream-beds in our neighborhood, but in only one— 

 that which flows through Highland Glen, near Chestnut Hill — have I ever noted 

 the presence of Eurynchium rusciforme (Neck.) Milde. In only one place on 

 rocks near the Wissahickon Creek have I detected non-fruiting patches of Tortella 

 tortuosa (L.) Limpr., and the hepatic Jubula pennsylva?iica (Steph.) Evans grows 

 to my knowledge in but one streamlet, where it covers perpendicular dripping 

 rocks. 



How are these anomalies to be explained? I have found Rhahdoweisia cris- 

 pata elsewhere no nearer than in the White Mountains of New Hampshire, Bux- 

 baumia aphylla very rarely anywhere else, Eurynchium rusciforme and Tortella 

 tortuosa elsewhere no nearer than the Delaware Water Gap, and Jubula pennsyl- 

 vanica in only that one glen beside the Wissahickon Creek. 



By painstaking explorations of our own neighborhood each of us may bring 

 to light many interesting facts in regard to the distribution of the bryophytes. 

 It is hoped that all members of our Sullivant Moss Society may be on the alert 

 and that, in future, they may have something to say concerning the rarities which 

 occur perhaps at the very threshold of their homes. 



508 Locust Ave., Germantown, Pa. 



