The Geographic Distribution of Pilea fontana 



F. J. Hermann 



In 1913 Dr. J. Lunell, proposing Adicea fontana as distinct 

 from the widespread A. pumila (L.) Raf., cited collections of his 

 new species from Benson County, North Dakota only. Rydberg, 

 having made the new combination for the plant necessitated by the 

 conservation of the name Pilea (Brittonia 1:87. 1931), later de- 

 fined its range as "N.D.-Nebr." (Flora of the Prairies and Plains 

 of Central North America. 1932). He maintained as likewise dis- 

 tinct, however, another of Lunell's segregates from Pilea pumila 

 (L.) Gray, namely P. opaca (Lunell) Rydb., but botanists of such 

 extensive field experience as Professor M. L. Fernald and Mr. C. 

 C. Deam have been unable to concur with Rydberg in his demarca- 

 tion of P. opaca from P. fontana. Pilea fontana, in its consistently 

 black achenes with prominent colorless margins (the achenes of 

 P. pumila being uniformly green and marginless), its relatively 

 small and short-petioled leaves with blades only 8- to 18-toothed 

 and rounded or truncate at the base rather than cuneate, seems 

 amply deserving of recognition, while P. opaca exhibits merely the 

 unstable characteristics of an ecologic variant. If P. opaca is con- 

 sidered as synonymous with P. fontana the combined range of the 

 two, according to Rydberg's account, will include Wisconsin. 



Recently Professor Fernald has appreciably extended the range 

 of P. fontana in delimiting it as "from North Dakota to Nebraska, 

 extending eastward to western New York" (Rhodora 38:170. 

 1936). The range of the species may now be further extended from 

 an examination of the North American Pilea collections in the 

 herbarium of the New York Botanical Garden and in the U. S. 

 National Herbarium, where typical material of P. fontana was 

 found from as far east as Prince Edward Island, Long Island and 

 northeastern New Jersey and from as far south as Florida. 



The known stations for Pilea fontana are still very few in com- 

 parison with those of the ubiquitous P. pumila, yet it is clear that 

 the former is by no means a species of limited distribution. More 

 general discrimination between the two by local botanists will 

 doubtless modify the present proportionate representation of these 

 two clearweeds in herbaria. An observation upon the difference in 



118 



