Jan. 1906] 
Cultures of Uredineae in 1905 
19 
June 15. A sowing of teleutospores from R. strepens 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 20-26/1,, and 
from R. strepens 17-21 by 24-30/1. 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. quadriddum 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) Prunus spinosa (blackthorn), P. divaricata (cherry- 
22 For previous cultures see Kellerman in Jour. Mycol. 9 : 107. 1903. 
23 Trav. Mus. Bot. Acad. Sci. St. Petersb. n: 67-69. 1905. 
