Robinson —Notes on the Genus Taphrina . 1 71 
some leaves of Rhus pyroides , Burch., from South Africa, which 
he ascribed to the presence of a parasitic fungus. He states, 
however, that from his dried material he could only make out 
several minute processes, on the surface of the leaf, resembling 
the basidia of an Exobctsidium. It seems not improbable 
that this form, on further investigation, may prove the same 
as our American species, especially as in his description of 
the changes in the infected leaves, Thomas speaks of a 
dense and palisade-like structure taken on by the spongy 
parenchyma. 
T. Potentillae (Farw.), Johanson. 
Exoascus deformans^ var. Potentilla , Farw., in Proceed- 
ings of Amer. Acad. vol. xviii (1883), p. 84. 
This distinct and well-marked species has been frequently 
found in various places in Massachusetts and Connec- 
ticut. Early in June it causes, on the leaves of Potentilla 
canadensis , L., little, roundish, yellow spots, which become 
convex above and concave beneath, and soon deepen in colour 
from yellow to brown and then to purple. Johanson, in 
describing the deformities produced by this species on P. Tor - 
mentilla , Scop., speaks of the swelling of the petioles and 
curling of the leaves ; but although I have looked over a 
number of dried and a few fresh specimens of P. canadensis , 
attacked by the parasite, I have not succeeded in finding any 
deformity in the petioles or stems. 
The peculiarities of the mycelium in this and the succeeding 
species have been noted already in the synopsis. The sub- 
epidermal position of the fertile threads naturally influences 
the form of the ascus so that the upper part only becomes 
expanded and contains the spores, while the lower portion is 
merely a very slender pedicel which, passing between the 
cells of the epidermis, connects the ascus with the mycelium 
below. In T. Potentillae the asci, which are borne on both 
sides of the leaf, are club-shaped and very slender. The 
spore-bearing portion is 25-33// l° n g and 8-10 // thick, while 
the slender pedicels, which are usually longer on the upper 
N 2 , 
