70 



Mycologia 



Melampsoropsis ledicola (Peck) Arthur 

 Peridermium decolorans Peck was found to be very common 

 on Picea, especially on Picea canadensis (Mill.) BSP., during 

 the summer of 1909. In the spring of the following year the 

 Ledum plants that were near the trees so richly infected by Per. 

 decolorans were kept under observation and telia were found 

 germinating about the first of June. The telia were then quite 

 conspicuous on the upper surface of the leaves. 



On June 7 sowings were made on four young trees of Picea 

 canadensis. Pycnia were evident on June 19 and aecia followed 

 in a short time. All the plants developed pycnia and aecia, but 

 the infection was sparing on two of them and pronounced on the 

 others. The aecia were determined as Peridermium decolorans 

 Peck. Two plants of Picea canadensis from the same place as 

 those used in the cultures were kept as controls and remained 

 free from aecia. 



The young shoots of Picea canadensis were just opening as the 

 telia of M. ledicola began to germinate in the field and not until 

 a week or ten days later did the buds of P. rubra and P. mariana 

 open. This may account for the Peridermium being much more 

 common on Picea canadensis than on the other species. 



The trees of Picea canadensis that grew beside the rusted Ledum 

 developed pycnia and aecia very abundantly ; the trees nearest 

 showed the richest infection, the aecia gradually diminishing as 

 the trees became more distant from the Ledum rust. A collec- 

 tion of the aecia was sent to Dr. Arthur, and was determined as 

 Peridermium decolorans Peck. During the summer several col- 

 lections of P. decolorans were made, and in every case Ledum 

 plants were found near, the leaves of which showed the spots 

 where the telia of M. ledicola had germinated in the spring. 



The aecia on P. canadensis were shedding spores by July 5. A 

 few collections of aecia were made on P. mariana during the 

 summer. 



Melampsoropsis Pyrolae (DC.) Arthur 



Rostrup has suggested that Peridermium conorum-Piceae 

 (Reess) Arth. & Kern is the aecial stage of this rust. Arthur 

 and Kern (Bull. Torrey Club 33: 432. 1906) state that the 



