POTATO BLIGHT (PHYTOPHTHORA INFESTANS) 357 
scattered about like spores. When the conidia germinate, 
instead of producing hyphae they produce zodspores, which, after 
swimming about for a few minutes, lose their cilia and begin to 
produce new hyphae. If favorably located, the new hyphae find 
entrance to a leaf through its stomata and start the disease anew. 
The odgonia and antheridia resemble those of Saprolegnia, but 
are produced on short hyphae 
within the tissues of the host. 
The odspore has a heavy wall 
and is not liberated until the 
tissues of the host surrounding 
it decay. “The odspores are well 
fitted to endure winter condi- 
tions, and as the dead leaves 
are scattered, the odspores con- 
tained are also scattered, and 
when freed it is probable that 
they often start the disease the 
following year. 
Potato Blight! (Phytophthora 
infestans). — This Fungus, com- 
monly called the Late Blight of 
the Potato, is a near relative of Fic. 308. — Reproduction in the 
the Grape Mildew. It attacks Downy Mildew of the Grape. a, 
the leaves, stems, and tubers conidiophores bearing conidiospores 
of the Irish Potato and is very the ends of their branches; 6, 
: . . . conidiospores; c, odspore; 2, ZO- 
rapid and destructive in its wesore. “Mucl- enlarged Ebon 
work. Figure 309 shows the Farmer's Bulletin 284, U.S. Dept. 
leaves of a Potato plant affected of Agriculture. 
with this disease. Like the 
Grape Mildew, after the mycelium is well established in the 
host, conidiophores are produced (Fig. 310). The conidia may 
grow directly into hyphae or produce zoéspores (Fig. 311). 
1 Late Blight and Rot of Potatoes. Circular 19, Cornell University Agr. 
Exp. Sta. 
ee of the Potato Fungus, Phytophthora Infestans. Bulletin 168, 
Vermont Agri. Exp. Sta. 
Germination and Infection with the Fungus of the Late Blight of Potato. 
Research Bulletin 87, Wisconsin Agr. Exp. Sta., 1915. 
Studies of the Genus Phytophthora. Vol. 8, No. 7, pp. 283-276, Jour 
Agr. Research, U. 8. Dept. Agr., 1917. 
