CULTURES OF SOME HETEROECIOUS 



RUSTS 



W. P. Fraser 



A region to the north of Pictou, Nova Scotia, offered such 

 excellent conditions for the study of many of the rusts that have 

 a Peridermium for their aecial stage, that recently some time has 

 been spent in their field study and a few cultures have been un- 

 dertaken. In this region there are extensive areas of young 

 coniferous woods with abundant growth of Ledum, Pyrola, Vac- 

 cinium, Rhododendron, Rubus, Myrica, and Chiogenes, and older 

 and more dense woods with the same species. A large area of 

 swamp also occurs with Chamaedaphne and other bog plants. 

 This region, which comprises several square miles, produced 

 many rusts, the following, as well as a number of others, being 

 collected : Melampsoropsis Pyrolae, M. ledicola, M. Cassandrae, 

 M. abietina, Pucciniastrum pustulatum, P. arcticum, P. Pyrolae, 

 P. minimum, P. Myrtilli, Calyptospora columnaris, and Cronar- 

 tium Comptoniae. Peridermium balsameum, Per. decolorans, Per. 

 columnar e, Per. Peckii, Per conorum-Piceae, Per. consimile, Per. 

 elatinum, and Per. abietinum were also common. 



Sowings were made on the various species of Picea used in the 

 culture experiments by first placing the leaves bearing telia in a 

 moist chamber, usually over night, until the teliospores had germi- 

 nated. These leaves were then suspended over the young trees 

 so that the basidiospores would fall on the young leaves of the 

 spruces, and the whole was then covered with a bell jar, usually 

 for two days. 



The young trees of Picea were obtained after the teliospores 

 had begun to germinate in the open, but they were selected some 

 distance from any source of infection. A considerable quantity 

 of earth was removed with the roots and they were then placed 

 in pots. Trees of about six to fifteen inches in height were se- 

 lected, and to prevent excessive transpiration a few branches were 

 removed. The experiments were carried on in a well-lighted 



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