398 Note on Discovery of the Rest-spores of the Potato-Fungus, 
under the name of oogonia for the larger, and antheridia for the 
smaller bodies. Mr. Smith perceived that he had discovered 
the sexual organs in this species of Peronospora, and continuing 
his observations he traced the relation between the two bodies. 
He observed the small antheridia attaching themselves to the 
(jogonia, and fertilising them, bj discharging part of their 
contents into the larger cells through a small tube which was 
protruded into the substance of the oogonia. The growth of the 
fertilised oogonium, now called an oospore, was traced by him 
until it arrived at maturity, when it is a spherical body covered 
with warts or coarse reticulations and of a black-brown colour. 
It is but slightly larger than the cells of the leaf, being about 
one-thousandth of an inch in diameter. 
When the rest-spores are mature, they separate themselves 
from the mycelium on which they grew, and lie as free bodies 
in the substance of the potato. And when in course of time the 
whole of the plant perishes, these small hardy bocMes remain, 
able to endure through the winter, and ready to renew the life of 
the destructive fungus with the restored vegetable life of another 
year. 
Mr. Smith has found the rest-spores in the haulm and tuber 
as well as in the leaf. 
Having thus discovered the means by which the fungus main- 
tains its life through the winter, we are able to look at the 
question of the possibility of doing something efficiently to 
mitigate if not destroy the evil. The malady which so exten- 
sively destroyed the silk-worms in the south of Europe some 
years ago, was unconsciously augmented by the producers throw- 
ing the dead worms together and keeping them within the 
establishment, thus increasing the conditions favourable to the 
growth of the fungus, and to the unlimited development of the 
spores. It was not until, by the advice of botanists, they cleared 
away from their silk-worm houses every dead insect and withered 
leaf, and cleaned the walls, that they got any master^ over the 
disease. So we have been unconsciously harbouring the potato 
disease in permitting the haulm and foliage to decay on the 
field or in dungheaps, which left the undecaying oospores behind 
ready to start into life when the proper conditions were present. 
Every care now should be taken to destroy by burning all 
diseased haulm ; and as dis(>ased tubers also harbour the rest- 
spores, these should be utilised in some way in which the spores 
could not be injurious, as by employing them in the manufacture 
of starch or British arrowroot. A vigorous and universal attempt 
thus to deal with the fungus might now greatly reduce the future 
liability to and extent of the disease, though it can never, I fear, 
deliver us entirely from it. 
