70 



Jan. 1906] Cultures of Urcdineae in 1905 1& 



June 15. A sowing of teleutospores from R. strep ens on R. cili- 

 osa May 8, and another June 7, gave no infection. 



Many writers, following Lagerheim, who received his clue 

 from Burrill, have made two species of the rusts on these two 

 hosts. It is true that the gross appearance, and to some extent 

 the microscopic characters of the two are perceptibly different. 

 These differences are shown, so far as the development went, in the 

 results of the cultures. The aecidial groups grown on R. ciliosa 

 were small and round, one to two millimeters across, without 

 noticeable hypertrophy of the tissues, and confined to the blade 

 of the leaf. On R. strepens, however, they took possession of 

 the veins, petioles and stems, and made large swellings from 20 

 to 25 millimeters long, and in one case the main steam for a 

 distance of ten centimeters or more was greatly swollen and dis- 

 torted. The differences also extended to the peridial cups and 

 to the spores. On R. ciliosa the cups were mostly one-half 

 millimeter high, and on R. strepens fully one millimeter high. 

 The aecidiospores from R. ciliosa measured 15-19 by 20-26/*, and 

 from R. strepens 17-21 by 24-30/*. These two cultures were 

 from the same source of infection, and must therefore be one 

 and the same species. Had uredospores and teleutospores been 

 raised, it is believed that the differences recorded in the books 

 for the two hosts would have been found. In short it is believed 

 that the differences of size and appearance are entirely due to the 

 influence of the hosts. The loose, somewhat succulent tissues of 

 R. strepens, and its vigorous habit of growth, are correlated with 

 the greater development of the fungus, while the firm close tis- 

 sues of R. ciliosa, not only prevent luxuriant development of the 

 parasite, but its parts become smaller throughout. These differ- 

 ences in the hosts also account for the failure to infect R. ciliosa 

 with spores from R. strepens, while the reverse process succeeded. 

 There appears to be no reason to doubt that under very favor- 

 able conditions the infection of R. ciliosa with spores from R. 

 strepens could be accomplished, and the resulting development be 

 the same as when the infecting spores came from R. ciliosa 

 itself. 22 



19. Puccinia Pruni-spinosae Pers. The Aecidium punc- 

 tatum Pers. {A. quadriiidum DC.) occurring in various parts 

 of the United States and Canada on different species of Anem- 

 one, Hepatica and Thalictrum so closely resembles the European 

 form which bears the same name, that little doubt has existed 

 of their genuine identity. In 1904 Dr. Tranzschel 23 of St. 

 Petersburg made cultures of this aecidium, sowing the aecidio- 

 spores from Aniemone coronaria on Amygdalus communis 

 (almond) Prunns spinosa (blackthorn), P. divaricata (cherry- 



22 For previous cultures see Kellertmn in Jour. Mycol. 9: 107. 1903, 

 M Trav. Mus. Bot. Acad. Sci. St. Petersb. //: 67-69. 1005. 



