42 MILDEWS, RUSTS AND SMUTS 
sometimes long and straight ; spores 20—25 X 12—15 p. 
Parasitic on plants belonging to Compositae, Scrophu- 
lariaceae, Ranunculaceae, Labiatae, etc. 
Sphaerotheca mors-uvae, Berk, and Curt. Mycelium 
persistent, at first white, then changing to a dingy brown 
colour, felt-like and readily peeled off the branches or 
fruit ; perithecia gregarious, more or less immersed in the 
mycelium, 76—no p diam., appendages usually few in 
number, pale brown, short, and contorted, sometimes 
elongated; ascus elliptic-oblong to subglobose; spores 
20 - 25 X 12 - 15 [JL. 
Syn. Erysiphe mors-uvae, Schwein. 
Parasitic on species of plants belonging to the order 
Ribesiaceae, as various species of Ribes. In this country 
it is known as the American gooseberry mildew, and is a 
very destructive pest to the gooseberry (Ribes grossularia), 
and has also occurred sparingly on the red currant (Ribes 
rubrum). The disease first appears as a white mildew on 
the young leaves and shoots, afterwards the fruit is attacked, 
and more or less covered with a dense brown felt. 
UNCINULA, Lev. 
Perithecia globose or somewhat depressed; asci several, 
containing 2—8 spores ; appendages usually simple, rarely 
once or twice forked, uncinate, that is, with a curl at the tip. 
The genus is readily distinguished by the uncinate tips 
of the appendages. 
KEY TO THE SPECIES 
A. Appendages branched 
aceris. 
B. Appendages simple (=unbranched). 
Appendages crowded, 100—150. Parasitic on species of 
Populus and Salix . salicis. 
Appendages variable in number, 12—60, rough. Parasitic 
on species of ■ Prunus . prunastri. 
Appendages few, generally about 15. 
Parasitic on Ulmus . eland estina. 
Parasitic on Vitis. . necator. 
Uncinula aceris, Sacc. Mycelium soon disappearing, or 
persisting as a thin, spreading film ; perithecia scattered 
or clustered, 120—225 p diam. ; appendages numerous, 
usually once forked, each branch sometimes again forked. 
