68 Journal of Agricultural Research voi. v, no. a 
fusely in these two host plants after they mature or are killed by the 
parasite, but the writer has been unable to find oospores in the young 
plants during the fall, and this agrees with Magnus's (9) report that 
oospores are not' produced in the seedling plants of spinach infected 
with Peronospora effusa in the fall. Magnus also states that the same 
is true in the case of Stellaria media and Veronica hederaefolia infected 
with Peronospora alsinearum and Peronospora grisea y respectively. 
The number of species of the genus Peronospora that may survive the 
winter in the mycelial stage are more numerous. Table II shows nine. 
Careful study is in progress in regard to the remaining species of this 
genus. As also shown in this table, there are three species of Plasmopara 
which may survive the winter in this stage, and this number, the writer 
is confident, will be increased by further studies. 
SUMMARY 
(1) There are at least several species of Peronosporaceae belonging to 
four genera that may be perennial in the tissues of their hosts, the myce¬ 
lium passing the winter either in the aerial or the underground organs of 
winter annuals, biennials, or perennials. 
(2) Phytophthora infestans is not an exception in the family to which 
it belongs as regards perennial mycelium. 
(3) The r 61 e of the mycelium of Phytophthora infestans in the tubers 
of its host is not an unusual one. It may grow from the tubers up the 
stem to the surface of the soil, sporulate, cause foliage infection, and 
bring about an epidemic of the disease. 
LITERATURE CITED 
(1) Bary, Anton de. 
1861. Die gegenwartig herrschende Kartoffelkrankheit, ihre Ursache und 
ihre Verhiitung. 75 p., 1 pi. Leipzig. 
(2) - 
1863. Recherches sur le d6veloppement de quelques champignons parasites. 
In Ann. Sci. Nat. Bot., s. 4, t. 20, p. 5-148, pi. 1-13. For translation 
see The potato disease. In Jour. Quekett Micros. Club, no. 22, 
P- I 39 “i 45 - *873. 
( 3 ) - 
1876. Researches into the nature of the potato-fungus—Phytophthora infes¬ 
tans. In Jour. Roy. Agr. Soc. England, s. 2, v. 12, p. 235-269, 8 fig. 
Reprinted in Jour. Bot. [London], v. 14 (n. s. v. 5), no. 160, p. 105- 
126; no. 161, p. 149-154. 
(4) Butler, E. J., and Kulkarni, G. S. 
1913. Colocasiae blight caused by Phytophthora Colocasiae Rac. In Mem. 
Dept. Agr. India, Bot. Ser., v. 5, no. 5, p. 233-261, pi. 1-4 (1 col.). 
(5) Istvanffi, Gyula de. 
1904. La perp6tuation du mildiou de la vigne. In Compt. Rend. Acad. Sci. 
[Paris], t. 138, no. 10, p. 643-644. Also in Rev. Vit., t. 21, no. 535, 
p.312. 
