16 Rhodora [JANUARY 
the characters of the uredo. The pseudoperidium of P. articum is 
described as “‘mammiformiprominulo, apice pertuso; cellulis apicis 
pseudoperidii aculeatis." This description applies accurately to the 
specimen in Vestergren but, if one glances at the figure of Dietel, 
which is a good representation of our species, the peridium could 
hardly be said to be even prominently mamillate. The aculeation of 
the peristomal cells is a character more common in species of Puc- 
ciniastrum than is generally supposed. When in good condition 
those cells in P. Potentillae Komarov are distinctly aculeate. In 
short our New England species is distinguished from the type of P. 
arcticum in which, as is shown by Vestergren no. 857, the peridium 
hardly projects beyond the epidermis, by its markedly conical shape 
and prominent corona. If we ask what are the variations in American 
specimens, I can say that after examining a large number of specimens 
I find a certain difference in the general appearance of the peridia 
but, except in the specimen from Grand Manan, I find none which 
agree with the European type. I should regard our fungus, however, 
not as a distinct species, since in most essential details it agrees with 
P. arcticum, but rather as a geographical variety or, if you please, 
race in which there is a more marked development of the pseudo- 
peridium. I would to distinguish it give it the name 
P. AncTICUM (Lagh.) Tranzs., var. americanum Farlow a Р. arctico 
typico pseudoperidio conico-truncato cellulis spinosissimis coronatis 
distinctum. 
Another Pucciniastrum very common on Potentilla tridentata of 
which the uredo has often been collected but to which there is scarcely 
any reference in mycological literature seems to me to be specifically 
undistinguishable from P. Potentillae Komarov. first described from 
Ninguta, Manchuria, on P. fragarioides in Jaczewski, Komarov & 
Tranzschel, Fungi Rossiae Exsiccati 7, no. 327, 1899. I first found 
it Sept. 1877 at Eastport and Portland on the Maine coast and since 
then I have found it on all the higher peaks of the White Mts. and as 
far south as Mt. Monadnock, N. H., and Berlin Mt. on the boundary 
between Massachusetts and New York, at Noonmark Mt. in the 
Adirondacks and I have specimens from White Fish Lake near 
Duluth collected by F. W. Dewart. It also occurs in Canada and 
specimens were distributed from Dr. J. Dearness in Fungi Colum- 
biani, no. 2367. Recognizing the resemblance of the uredo to U. 
