Arthur and Kern : Peridermium 429 



Aug. 27, 1904, E. W. D. Hoi 



W. D. Holway 



On Pice a sitchensis (Bong.) Carr., Seldovia, Alaska, August 

 12, 1904, C. V. Piper, communicated by P. L. Ricker. 



On Pice a canadensis (Mill.) B. S. P., Kenai, Alaska, August 18- 

 20, 1904, C. V. Piper, communicated by P. L. Ricker. 



A common species northward, of an essentially alpine charac- 

 ter. It occurs on the summits of the Adirondack and White 

 Mountains, islands of the Atlantic coast from Mt. Desert to New- 

 foundland, and along the mountains of the Pacific coast from 

 Banff, British Columbia, into Alaska. The species is especially 

 marked by its very large spores, being much larger than of any 

 other American Peridermium. 



In 1882 and 1883 Dr. W. G. Farlow explored the subalpine 

 summits of the White Mountains with the especial object in view 

 of ascertaining the distribution of the species of Peridermium, and 

 "their proximity to certain teleutosporic forms on Ericaceae" He 

 discussed the results of his observations at considerable length in 

 a paper before the Appalachian Club,* in which he concluded that 

 Per. color ans was sufficiently like Per. abietinum of Europe to be 

 considered synonymous, especially when taken with the known 

 distribution of the rust on Ledum, which had recently been shown 

 by De Bary to be the telial form. This conclusion was accepted 

 by German botanists, as well as American, and a collection made 

 on Mt. Washington, New Hampshire, was issued in Rabenhorst's 

 Fungi Europaei under the name " Cluysoniyxa Ledi (A. & S.)." 

 In the score of years since these observations were made much 

 knowledge of the distribution of rusts has accumulated, and it is 

 now apparent that there are two species of rusts on Ledum, and 

 that it is [/redo ledicola Peck, with which the distribution of Per. 

 decolorans corresponds, and not with the one common to Europe 

 and America, generally called Chrysomyxa Ledi. Moreover, the 

 spores of Per. decolorans are very much larger than those of Per. 

 abietinum, a difference corresponding with the difference in size of 

 the uredospores of the two forms on Ledum. We believe, in fact, 

 that judging both from structural characters and geographical dis- 

 tribution, Per. decolorans is the aecial form of what in most her- 

 baria is called [/redo ledicola. 



*Appalachia 3 : 239-243. 1884. See also Proc. Am. Acad. 20: 320. 18S5. 



