198 



Mycologia 



An interesting feature of the pycnial stage of the Melampsorae 

 is a pronounced and characteristic odor evident at the time the 

 pycnia are expelling spores. Exudations of a clear liquid also 

 accompany this stage and are found to be sweet to the taste. 

 These characters are possessed by the pycnial stage of a number 

 of other forest trees and field plant rusts. The odor of the 

 pycnial stage of M damps or ella elatina (A. & S.) Arth. on Abies 

 spp., Peridermium coloradense (Diet!.) A. & K. on Picea engei- 

 mamu, and Puccinia monoica (Pk.) Arth. on Arabis kochii is 

 particularly noticeable. The pycnial odor of the Mdampsorae is 

 fragrant, while that of Peridermium coloradense is decidedly of- 

 fensive, approaching the odor given out by certain Nymphaeas. 



Summary 



The results of the present investigation show that the rusts on 

 Populus which were heretofore distinguished as Melampsora 

 medusae and M. albertensis will infect both Pseudotsuga and 

 Larix. In the absence of sharp differential characters between 

 these two forms, both in their gross and minute details, it is sug- 

 gested that they are the different host manifestations of the same 

 rust and should apparently be referred to Melampsora medusae 

 Thiim. 



Two new hosts for this rust are recorded, viz., Larix lyalli and 

 Pseudotsuga macrocarpa. 



New and interesting features attending the production of 

 pycnia in the Melampsorae are reported. 



Office of Investigations in Forest Pathology, 

 Bureau of Plant Industry, 

 Missoula, Montana. 



