MILDEWS, RUSTS AND SMUTS 19 
the stomata, 70—130 X 8—10 pi, with a few quite short 
branches near the tip, some of the branches remain simple, 
others bear 2—3 short branchlets, the tips of which are 
truncate after the oospores have fallen away; conidia 
broadly elliptical, or broadly pear-shaped, with an apiculus 
or wart at the base, colourless, size variable, 25—40 X 
18—25 (X ; oospore unknown. 
Syn. Peronospora pusilla, De Bary. 
Parasitic on living leaves of Geranium pratense, G. phaeum, 
G. silvaticum and other species. 
Plasmopara densa, Schroet. Tufts usually small, dense, 
scattered or confluent, white, becoming tinged yellow with 
age ; mycelium with vesicular haustoria ; conidiophores 
emerging in tufts through the stomata, 150—180 x 8—10 
p, dividing upwards into two or three main branches, 
each of which bears i—3 branchlets ; conidia broadly 
elliptical, or sometimes almost globose, in other examples 
broadly lemon-shaped, minutely and bluntly warted at the 
tip as a rule, 17—23 X 12—17 p, colourless ; oospore yel¬ 
lowish, 25—35 p diam. 
Syn. Peronospora densa, Rabenh. 
Peronospora nivea, Unger. 
Parasitic on plants belonging to the order Scrophularia- 
ceae, Bartsia, Euphrasia, Pedicularis, Alectorolophis, etc. 
Plasmopara viticola, Berl. and De Toni. Spots on the 
upper surface of the leaf at first yellowish-green, then 
brownish and becoming dry; on the under surface, on 
areas corresponding to these spots, a delicate white mould 
is present, more especially towards the circumference; 
conidiophores emerging in tufts from the stomata, soon 
spreading, base thickened, 250—500 x 9—12 p, simple 
for some distance, then with 4—^5 main branches spreading 
almost at right-angles, these each bear 3—4 opposite pairs 
of shorter branches, each of which in turn, bears 2—^4 short 
branchlets at the tip, on which the conidia are borne ; 
conidia broadly elliptical or sometimes almost globose, 
colourless, size variable, 18—30 X 12—17 p, producing 
zoospores on germination ; oospores globose, smooth or 
more or less marked with slightly-raised veins, 30—^35 p 
diam. 
Syn. Botrytis viticola, Berk. 
Peronospora viticola, Casp. 
Parasitic on plants belonging to the order Vitaceae, 
