270 
Journal of Mycology 
[Vol. 11 
ROSTOVTSEV, S. I. CONTRIBUTIONS TO THE KNOWL¬ 
EDGE OF THE FALSE MILDEWS (PERONO- 
SPORACEAE.) 
Bulletin of the Moscow Agricultural Institute, 1903. 
Part 1. 24 pp., 20 figures. 1 (Russian.) 
A REVIEW BY ERNST A. BESSEY. 
In October, 1902, the author received specimens of cucum¬ 
ber leaves from Tver government, which were found to be suf¬ 
fering with a form of what has been known as Peronospora 
cubensis. He reviews some of the literature of this species and 
points out that of the two species parasitic on Cucurbitaceae, 
Plasmopara australis is a typical Plasma para, both as regards 
conidiophore and germination of conidia, and differs from P. 
cubensis. The latter possesses conidiophores like Peronospora. 
The conidia, however, have an apical papilla and germinate some¬ 
times with the production of zoospores, thus showing the char¬ 
acters of Plasmopara. He proposes to found for this species 
a new genus to be known as Pseudoperonospora with the one 
species P. cubensis. The chief characteristics of this genus are 
possession of a conidiophore like Peronosport and conidia like 
Plasmopara. The Russian fungus he distinguishes from the 
typical species as the variety Tweriensis. The differences lie 
in the appearance of the spots and more especially in the fact 
that in the former the conidiophores are single, in the latter, 
two to six together. 2 The author finds that the conidia are 
borne on very slender, very short stalks separating them from 
the ends of the conidiophores. These same pedicels occur also 
in various species of Peronospora, Plasmopara, Bremia, Phy- 
tophthora and Cyst op ora studied by the author. They remain 
unstained by iodin and sulfuric acid or by chloriodid of zinc, 
while the conidia and conidiophore are stained blue. These 
pedicels dissolve in water, setting the conidia free. Germina¬ 
tion of the conidia occurs sometimes by germ tubes, sometimes 
by the formation of zoospores. 
Immature oospores are found in old dead leaves late in the 
autumn. 
A few months latter the author published in Germany 1 a 
similar article giving again the description of this fungus and 
1 The work is entitled in Russian: Rostovtsev, S. I. Materiali k 
poznaniu lozhnomutchnerosnykh gribov (Peronosporaceae). Otdyel’nye 
ottiski iz “Izvyestii Moskovskavo Syel’skokhozya-istvennavo Instituta” kn. 
1 zo 1903 god. 
2 See below for further discussion of this proposed variety. 
1 Rostowzew, S. G. Beitrage zur Kenntnis der Peronosporeen. 
Flora oder Allgemeine Botanische Zeitung, 92\ 405-430. 1 fig. pi. 11-13. 
Oct. 1903. 
