304 



Mycologia 



Cultures in 191 7 



No trips for observation were taken during this year, and the 

 usual amount of time bestowed on the cultures was greatly re- 

 duced. About 25 collections with resting spores and 6 with 

 active spores, the latter all forms of Aecidium, were available 

 for the tests. About 120 drop cultures were made from the 

 sets of resting spores, showing that 15 of the collections were 

 more or less viable at the time. From the fifteen collections 14 

 successful inoculations were secured, 103 sowings having been 

 made. The work was partly done by Mr. C. C. Rees and partly 

 by Dr. E. B. Mains, members of the laboratory staff. 



Negative Results in 191 7. — It seems worth while to call 

 attention to three attempts which wholly failed, with the hope 

 that some one may be aided in solving the problems involved. 



1. Puccinia triticina Erikss. on Triticum vulgar e Mill, was 

 obtained from the border of a wheat field in September, 1916, by 

 Mr. C. C. Rees, and sown on Clematis Flammula L., May 17 

 following, but with no result. The teliospores, however, were 

 germinating very feebly. The conclusion was reached some two 

 years ago from morphological and other data, that the common 

 leaf rust of wheat is a race of the common P. Agropyri E. & E., 

 occurring upon many wild grasses. P. Agropyri from Agro- 

 pyron glaucum was cultured on Clematis Vitalba L. in Germany 

 by Dietel in 1892. In America cultures have shown races to 

 exist in eastern United States between Bromus ciliatus and 

 Clematis virginiana, in Colorado between Elymus canadensis and 

 Agropyron Smithii and C. ligusticifolia, in Texas between Elymus 

 virginicus and C. Drummondii, and in North Dakota between E. 

 canadensis and Anemone cylindrica. As Clematis Flammula and 

 C. Vitalba are almost the only common Ranunculaceous plants 

 through the wheat growing regions of southern Europe, northern 

 Africa and western Asia, an area that probably includes the home 

 of the original wild wheat, the assumption is reached that one or 

 both these hosts can be made to bear aecia from P. triticina under 

 favorable conditions. 



2. Puccinia emaculata Schw. on Panicum capillar e L. was 

 sown May 8 on Euphorbia corollaia, and May 9 on E. commutata 



