PAPERS GIVING RUSTS OF NORTH AMERICA. 177 



Among the innovations introduced by Link and adopted by 

 Schweinitz in his later work was the use of the genus Ccconm to in- 

 clude what had before passed under the genera Uredo, ^cidium, 

 Peridermium, etc. These older genera were only half ingested, 

 however, and a sort of double generic name was made, that is, the 

 genus and subgenus were used together: it was C<2oma {Uredo), 

 Cccoma (JEcidium), etc. But this proved too clumsy for general 

 use, and we find Schweinitz constantly reverting to the older nomen- 

 clature in his comments, as under 2887, Cccoma (Alcidium) lumi- 

 natum, he speaks of "this ^cidium," not of this Cccoma, or of this 

 Cccoma (Jlcidium). Link's genus Cccoma never found much sup- 

 port, and eventually fell into disuse, although the older application 

 of the name as a genus coordinate with Uredo, ^cidium, etc., is 

 still in favor, these names in the most modern usage constituting 

 form-genera. In the list of species placed by Schweinitz at the end 

 of the volume, as those first detected by him in America, he lists 

 ^cidium, Ceratites and Peridermium with initial rank, each with 

 Cccoma as subgenus, leaving Cccoma as a genus to include only the 

 one subgenus, Uredo, thus indicating some revolt, or at least incli- 

 nation to deviate from Link's method. That the form of name 

 given in the final list was no careless indexing but the conclusion of 

 mature judgment seems certain from the use of one of these names 

 in the description of 2932, P. investita, where he speaks of " ^cidium 

 gnaphalitatum," the name in the final list, and not of Cccoma Gnaph- 

 aliatum, as given in the body of the work under 2873. 



Another unfortunate innovation by Link faithfully adopted by 

 Schweinitz was the change of specific names having the form of a 

 proper noun, usually in the genitive singular, to the form of an ad- 

 jective. Thus ^cidium Galii became Cccoma galiatum, A. Ber- 

 beridis became C. berberidatum, A. Violcc became C. violatum, and 

 so on for a dozen or so well-known names, and to this list Schwei- 

 nitz added many more, i. e., Cccoma pyrolafum, C. hepaticatum, C. 

 myricatum, C. dracontionatum, C. houstoniatum, C. pedatatum, C. 

 dematitatiim, C. helianthatum , C. track elifoliatum and eighteen or 

 twenty more, all of them again listed under "^cidium (Cseoma)" 

 at the end of the volume. These changes with few exceptions were 

 made under the genus Cccoma. Link changed a few specific proper 



