502 RESEARCHES ON FUNGI 



Winnipeg, I gathered some haulms of the cultivated Oat {Avena 

 saliva) which had been produced in the previous summer and which 

 bore a large number of teleutospore-sori of Puccinia graminis. The 

 Oat plants had been exposed to the weather during the whole of a 

 long and severe winter, such as is normal for Manitoba. The tem- 

 perature had often remained for periods of several days below 0° F. 

 and had sometimes descended to between — 30° and — 40° F. Owing 

 to the persistently low temperature during the winter and to the 

 subsequent dry weather of the spring, none of the teleutospores 

 had germinated. In order to provide conditions for germination, 

 pieces of Oat stems bearing teleutospore-sori were placed so that 

 they floated on the surface of drops of distilled water set on glass 

 slides. The slides were then enclosed within a Petri dish. The 

 teleutospores were by this means supplied with water without bemg 

 submerged. As a rule the preparations were riiade in the evening. 

 During the ensuing night the teleutospores germinated, and in the 

 morning an abundance of basidia with sterigmata and basidiospores 

 could be observed. The teleutospore-sori, after germination had 

 set in, were examined under the low and the high powers of the 

 microscope. Due care was taken to prevent rapid evaporation 

 from the basidia by surrounding each preparation with a glass ring 

 and by covering in the space between the top of the ring and the 

 sides of the objective of the microscope with moist blotting paper. 



The teleutospore of Puccinia graminis is two-celled, and each 

 of the cells can give rise to a basidium. A basidium, as it grows 

 outwards from the teleutospore-sorus, elongates at its apex and 

 becomes curved at its free end. The free curved end of a basidium 

 becomes divided by septa into four cells, which are more or less 

 equal in size and contain approximately equal amounts of proto- 

 plasm. Each cell develops a sterigma and a single spore. The 

 four spores of a single basidium usually develop simultaneously. 

 A spore begins its development in the same manner as that of one 

 of the Hymenomycetes, i.e. a hilum is first developed and the body 

 of the spore takes up a lateral position at the end of the sterigma 

 (Fig. 203, a, b, c, d). After a spore has attained its full size, all 

 the protoplasm of the cell with which its sterigma is connected 

 (presumably with the exception of a very thin lining layer) creeps 



