2 BULLETIN 241, U. S. DEPARTMENT OF AGRICULTURE. 



new species, Peridermium beilieli (6). The type material P. pyri- 

 forme was not accessible at the time the article was prepared, as all 

 of Peck's specimens were packed up and in transit from the old to 

 the new quarters of the New York State Museum. The writers there- 

 fore had to depend upon Arthur and Kern's published statement con- 

 cerning this species (1, p. 420). The spore measurements also of the 

 typical P. pyriforrne did not correspond, since the length of spores of 

 the eastern species as given by Peck in his original description was 

 too great. While this article by the writers (6) was in press, Arthur 

 and Kern published an article (2) in which they discarded their earlier 

 interpretation of P. pyriforrne and admitted that there is a species of 

 Peridermium with typical "pyriform, obovate, or oblong-pyriform 

 spores," just as Peck had originally described it in 1875 (10), and 

 that their original assignment of P. pyriforrne Peck to what is now 

 known as P. comptoniae was an error. They also suggested that the 

 alternate stages of this Peridermium would probably be found on 

 species of Comandra. 



Orton and Adams (9), in 1914, published an article on Peridermium 

 from Pennsylvania, in which they discussed Peridermium comptoniae 

 and P. pyriforrne. They described the finding of a caulicolous species 

 of Peridermium at Charteroak, Huntingdon County, Pa., on the 

 trunks of Pinus pungens, which proved to be the true Peridermium 

 pyriforrne of Peck. Subsequently Cronartium comandrae was found 

 within 40 feet of the infected pines and the conclusion reached that 

 this Cronartium is the alternate stage of Peridermium pyriforrne. 

 They also state that P. beilieli is probably a synonym of P. pyriforrne. 

 In May, 1914, Arthur and Kern in a general discussion of the North 

 American species of Peridermium inhabiting pines (3) gave the syn- 

 onymy of P. pyriforrne, a technical description, and an explanation 

 of their change of opinion regarding the species. 



In June, 1914, the writers published culture data (8) showing that 

 successful sowhigs of the seciospores of Peridermium pyriforrne had 

 been made on Comandra umbellate, thus completing the life cycle of 

 this interesting rust and proving that its alternate stage was the 

 Cronartium found on Comandra. 



MORPHOLOGY OF THE FUNGUS. 



The macroscopic characters of Peridermium pyriforrne are practi- 

 cally identical on all the hosts examined by the writers, but there 

 are some differences in the microscopic characters, especially in the 

 shape and size of the seciospores. This difference in size and shape 

 of the spores may be due to the influence of the secial host; that is, 

 they may vary according to the species of Pinus which the Perider- 

 rium inhabits. In specimens of the rust on Pinus contorte (PI. I, 



