406 Arthur and Kern : Peridermium 



tospora, so abundant and conspicuous on Vaecinium, in this coun- 

 try extending from the Atlantic to the Pacific coasts. Twenty 

 years ago, in 1885-6, Julius Kuhn* sowed the spores of this rust 

 upon European spruces in the experimental garden of the Uni- 

 versity of Halle, and at the same time upon the American species, 

 Abies balsamca Mill., A. nohilis Lindl., A. Fraseri Pursh, A. con- 

 color L. & G., and A. magnified Murr., in all cases raising the 

 Per. columnare, which Kuhn had previously shown belonged to 

 the species ; and yet to this day no American collection of Peri- 

 dermium can with certainty be assigned to the species. There is 

 assuredly an attractive field for culture work here, and one which 

 derives importance both from the economic and scientific sides. 



Although it is not possible to distribute the American species of 

 Peridermium with their respective telial forms, yet some approach 

 toward this end can be made by distributing them among telial 

 genera. So far as we know, no attempt of this kind has hereto- 

 fore been made, but we believe that our studies warrant us in as- 

 signing with some degree of probability the form-species of Peri- 

 dermium, which we are able to distinguish morphologically, to 

 seven prominent telial genera, or to six, if Calyptospora be con- 

 sidered a synonym of Pucciniastnim, as some would have it. The 

 genus Mel amps oridium is included in this connection, although no 

 Peridermium has yet been found in North America that can be as- 

 signed to it. The name u Chrysomyxa" is used in the customary 

 sense, but as we believe, not in its true application, this being 

 indicated by the quotation marks, the better generic name being 

 Melampsoropsis. The accompanying table exhibits the distribu- 

 tion and the underlying characters. 



We have found the most important character for assorting the 

 species into groups to be the position of the pyenia, whether sub- 

 cuticular or subepidermal. After this comes the shape of the 

 aecia, whether cylindrical, or flattened laterally and tongue-like, 

 the forms on Pinns being kept distinct from those on other Conif- 

 erae. There still remain the bark-inhabiting forms, all on Pinus 

 so far as known, which have peridia differing from those of all 

 other aecia in being tissue-like and more than one cell thick. 

 These characters may be arranged in the form of a key, as follows : 



* Hedwigia 26 : 28. 1887. 



