34 
MILDEWS, RUSTS AND SMUTS 
Peronospora sparsa, Berk. Patches of mildew whitish, 
indistinct; conidiophores scattered, slender, 250—400 X 
6—8 [ji, divided into 3—5 primary, ascending branches, 
which become 2—4 times irregularly forked, sometimes 
the branches are slightly curved and bent backwards, 
ultimate branchlets generally curved and tapering to a 
point ; conidia broadly elliptical, tip rounded, 17—22 X 
14—18 p, almost colourless. 
This species occurs on the leaves of plants belonging 
to the order Rosaceae, and so far only on the genus Rosa. 
It sometimes proves very destructive to roses, more 
especially when grown under glass. 
C. Undulatae 
Peronospora ficariae, Tub Forming broadly effused, 
dingy white, then greyish-lilac patches of mildew ; conidio¬ 
phores tufted, 200—400 X 8^—^10 p, 5—7 times equaliv 
or unequally forked, the last two orders of branches oken 
curved or wavy, ultimate branchlets often tapering to a 
point ; conidia broadly elliptical, 20—29 x 15 —20 p,, 
pale dingy lilac ; oospores angularly globose, wall brown, 
almost or quite smooth, 30—35 p diam 
Syn. Peronospora grisea, Unger. 
Peronospora myosuri, Fuckel. 
Parasitic on leaves of plants belonging to the order Ranun- 
culaceae, as Ranunculus ficaria, R. acris, R. -flammula, R. 
auricomus, R. bulbosus, R. repens, etc. 
Often covering the entire plant, and producing fruit 
everywhere, except on the roots and flowers. 
Peronospora urticae, De Bary. Forming greyish-lilac 
patches of mildew ; conidiophores 200—300 x 8—g p, 
4—6 times forked above, branches wavy, ultimate branch- 
lets tapering to a point, often curved downwards ; conidia 
broadly elliptical or subglobose, 20—28 x 17—22 p, tip 
rounded, pale dingy lilac ; oospores subglobose, brown, 
smooth, 21—32 p diam. 
Parasitic on plants belonging to the order Urticaceae, 
as Urtica dioica and U. urens. 
Forming small greyish-lilac patches on the under surface 
of the leaves. 
Peronospora alta, Fuckel. Forming greyish-violet, vel¬ 
vety patches ; conidiophores generally solitary, rarely in 
tufts of 2—3, slender, 200—600 x 8—9 p, 6—8 times 
forked upwards, branches spreading, more or less curved, 
