Fraser: Cultures of Heteroecious Rusts 189 



third sowing on June 21 gave pycnia on June 30 with aecia on 

 July 8. Two more sowings were tried on Larix laricina without 

 result. 



The teliosporic material was collected from a grove of young 

 poplars that were severely attacked by the Melampsora the pre- 

 vious season. A visit to the place showed that several young 

 trees of Tsiiga canadensis grew among the poplars and these were 

 carefully watched for the appearance of aecia. Pycnia and aecia 

 were first collected on June 19. A very rich infection of the trees 

 of Tsuga in the immediate vicinity soon followed. The young 

 trees about a foot in height, beneath which were many poplar 

 leaves with the telia of the Melampsora, showed an exceedingly 

 rich infection, practically all the leaves and many of the twigs 

 iDeing infected. The poplars were also watched and in due time 

 the uredinia of the Melampsora appeared. The distribution was 

 such that it indicated the source of infection to be the Caeoma on 

 the Tsuga. Similar observations were carried out at Truro, but 

 the place could not be visited often and the observations were not 

 so complete. The observations and cultures leave no doubt in 

 the mind of the writer that the Melampsora on Populus in 

 the region studied by the writer has aecia on Tsuga canadensis, 

 and that the aecia are Caeoma Ahietis-canadensis. It seems 

 probable that the species discussed is a form of Melampsora 

 Medusae with aecia on Tsuga canadensis. The weak pycnial 

 infection of Larix in one culture seems to support this view 

 l3ut further study is needed. The field collections of aecia were 

 ■submitted to Dr. Arthur, who confirmed the determination. 



A Caeoma was often collected in this region on Larix laricina. 

 As there seem to be no good characters for separating the aecia 

 •of Melampsora Medusae and M. Bigelozmi, both of which have 

 been shown by cultures to occur on Larix^ it was impossible to 

 determine to which species these collections belonged. The field 

 evidence, though not very strong, indicated that all the collections 

 'On Larix belonged to Melampsora Bigelozvii Thiim. 



Peridermium balsameum Peck 



This Peridermium was found abundantly on Abies balsamea 

 (L.) in all the regions of Nova Scotia visited by the WTiter. 



