Oct. ii, 191s Perennial Mycelium in Species of Peronosporaceae 67 
Table II .—Species of Peronosporaceae having perennial mycelium 
Name of fungus. 
Name of host. 
Authority. 
Phytophthora infestans 
Do. 
Do. 
Phytophthora cactorum 
Cystopus candidus .... 
Do. 
Plasmopara viticola ... 
Plasmopara pygmaea .. 
Plasmopara halstedii .. 
Peronospora dipsaci ... 
Peronospora schachtii. 
Peronospora alsinea- 
rum. 
Peronospora grisea . 
Peronospora effusa .... 
Do.. 
Peronospora ficariae ... 
Do. 
Peronospora parasitica 
Peronospora viciae .... 
Peronospora rumicis .. 
Solanum tuberosum ... 
_do. 
....do. 
Panax quinquefolium . 
Capsella bursa pastoris. 
Lepidium virginicum.. 
Vitis vinifera . 
Hepatica acutiloba .... 
Helianthtis diversicatus. 
Dipsacus fu llonum . 
Beta vulgaris . 
Stellaria media . 
Veronica hederaefolia .. 
Spinacia oleracea . 
A triplex hortensis. 
Ranunculus ficaria .... 
Ranunculus fascicula- 
ris. 
Lepidium virginicum .. 
Vida sepium . 
Rumax acetosa . 
De Bary f 1), 1861, Bonn, Germany. 
Jensen (6), 1887, Nerilly, France. 
Melhus (12), 1913, Houlton, Me. 
Rosenbaum (14), 1914, Ithaca, N. Y. 
Melhus (12), 1913, Madison, Wis. 
Do. 
Istvanffi (5), 1904, Budapest, Austria. 
Stewart (15), 1910, Ithaca, N. Y. 
Melhus (12), 1913, Madison, Wis. 
Kiihn f8k 1875, Halle, Germany. 
Kiihn (7), 1872, Halle, Germany. 
Magnus (9), 1888, Berlin, Germany. 
Do. 
Do. 
Do. 
De Bary (3), 1876, Bonn, Germany. 
Melhus (12), 1913, Madison, Wis. 
Do. 
Melhus (13), 1915, District of Colum¬ 
bia. 
De Bary (3), 1876, Bonn, Germany. 
There can be no doubt that the mycelium of several species of Perono¬ 
sporaceae may become perennial. Of course this can take place only when 
the host is a winter annual, biennial, or perennial, and quite generally 
infected. Such plants may live through the winter and renew activity 
in the spring, when the fungus may sporulate and spread the disease. 
The perennial nature of the mycelium of other species of the genus 
Phytophthora has not been studied critically, but there is reason to 
believe that Phytophthora infestans is not the only one that may become 
perennial. In many cases other species produce oospores prolifically. 
Butler and Kulkarni (4) believe that on Colocasiae Phytophthora 
colocasiae may survive the dry seasons of India in the mycelial stage. 
Another case of perennial mycelium is that of Phytophthora cactorum 
on ginseng ( Panax quinquefolium ), a perennial having a fleshy root, 
described by Rosenbaum (14). The Phytophthora fungus flourishes on 
the roots, and, according to this author (14), can spread from the roots 
up the stem to the surface of the soil, and produce conidia which infect 
the foliage, a case very analogous to Phytophthora infestans . 
Table II shows that, so far as known, only one species of Cystopus has 
perennial mycelium—that is, Cystopus candidus on two hosts, Lepidium 
virginicum and Capsella hursa pastoris . Both of these plants may be 
either annuals or winter annuals, and in both the fungus may become 
systemic and may survive the winter, provided the host plants live. 
Unlike Phytophthora infestans , Cystopus candidus produces oospores pro- 
