MILDEWS, RUSTS AND SMUTS 
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erect, 300—500 X 8—10 [x, repeatedly forked upwards, 
ultimate branchlets spreading, straight as a rule ; conidia 
broadly elliptical or broadly pear-shaped, tip rounded, 
dingy greyish-violet, 18—28 X 15—18 p,; oospore globose, 
yellowish brown, warted, or with' irregular raised ridges, 
which sometimes show a tendency to form an irregular 
network here and there, 35—40 p. diam. 
Syn. Peronospora conferta, form agrostemmatis, Fuckel. 
Parasitic on caryophyllaceous plants, as Silene, Dian- 
thus, Agrostemma, etc. 
Peronospora arenariae, De Bary. Forming dense tufts 
of mould of a greyish-white colour ; conidiophores emerging 
singly or in small tufts, through the stomata, slender, 250— 
450 X 8 —10 p,, repeatedly forked above, ultimate branch- 
lets spreading, straight or slightly curved ; conidia elhp- 
tical, colourless, 14—17 x 9—^13 p,; oospore globose, wall 
chestnut brown, covered with stout hemispherical warts, 
sometimes mixed with others more cylindrical in form, 
30—35 p, diam. 
Syn. Botrytis arenariae, Berk. 
Peronospora conferta, Unger. 
Parasitic on plants belonging to the order Caryophylla- 
ceae, as Stellaria media, Arenaria serpyllifolia, A. trinervis, 
etc. 
This species is closely allied to Peronospora dianthi, and 
by some authors is considered as only a form of that species. 
It differs in the whitish colour of the patches of mould, 
and the colourless conidia. 
Peronospora polygon!, Thuemen. Patches of mildew 
dense, effused, dingy violet ; conidiophores emerging 
through the stomata, usually in considerable numbers, 
320—420 X 9— II p,, repeatedly forked above, branches 
of the second and third orders usually spreading and curved ; 
conidia of an elongated elliptical shape, or slightly narrowed 
below and with a tendency to become pear-shaped, 30—^40 
X 15—20 p,, tinged greyish. Oospores unknown. 
Parasitic on leaves of plants belonging to the order 
Polygonaceae, as Polygonum convolvulus, P. aviculare, etc. 
Differs from Peronospora rumicis, which grows on plants 
belonging to the same order, in having larger, and paler 
coloured conidia. 
Peronospora calotheca, De Bary. Tufts of mildew soft 
and greyish; conidiophores rather slender, generally 
