29t& 



17 Mycologia 



slight difference in size of the urdiniospores, and, of course, in 

 the teliospores a difference in number of cells and consequent 

 size. He points out, however, that these differences are such as 

 are to be expected in other similar cases. The comparison of 

 these two forms of Distichlis rust, as to morphology, hosts and 

 distribution, is an interesting topic, which need not be pursued 

 further here. 



If the Carex-Aster-Solidago-Erigeron studies supplemented by 

 studies with the Distichlis rust, opened up new views of the 

 species question in relation to host influence and teliosporic di- 

 morphism, so did the Carex-Ribes studies disclose new views in 

 another direction. The first cultures were in 1901. As the 

 results of sowing teliospores on Ribes gave peculiarly small and 

 pale aecia, it was thought that an unrecognized species had been 

 found, which was called Puccinia albiperidia. Whether this 

 form was distinct from the common Carex-Ribes rust of the 

 fields, distinguished as P. Grossulariae, and whether American 

 forms were distinct from European forms, of which Klebahn had 

 recognized five, were questions which received attention from 

 year to year as opportunity permitted. In this study Dr. Klebahn 

 graciously consented to lend assistance, and during the two sea- 

 sons of 1904 and 1906 made cultures at Hamburg, Germany, 

 from telial material supplied by the writer. 



Just as the problem seemed solved, and Dr. Klebahn 6 and my- 

 self had independently arrived at the conclusion that in both 

 Europe and America only one heteroecious species occurred, 

 which possessed a number of strains or races, it was discovered 

 by C. R. Orton, 7 while assisting with the rust studies, that the 

 original material of P. albiperidia onCarex pubescens, as well as 

 that on a number of American species of Carex similar to C. 

 gracillima, possessed urediniospores with only one basal pore, in 

 part at least, instead of the usual three or four equatorial pores. 

 Again the Carex-Ribes rusts of Amercia seemed to fall into two 

 species, not based on differences in the aecia this time, but on dif- 

 ferences in the urediniospores. From 1910 onward the question 

 in this connection was whether or not the same species of rust 



6 Zeits. Pflanzenkr. 17: 132-134. 1907- 



7 Mycologia 4: 14, 200. 1912. 



