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renders it all the more objectionable and difficult to com- 
bat. When wilted plants are pulled up, the parts of the 
stem a few inches above the level of the ground are found 
to be blackened and often decaying ; these symptoms have 
given the disease its popular name. 
The parasitic fungus which causes the aster disease, 
unlike Phytophthora infestans of the potato, never attacks 
the leaves directly but enters the plant from the soil 
through the root of the seedling. Once within the young 
plant it may, either grow slowly not seriously interfering 
with the work of the vital parts of the seedling, or it may 
extend rapidly through these and cause immediate col- 
lapse. Mucroscopic examination of the blackened portion 
of the stem shows the distribution of the fungus in the 
tissues. The cells of the rind as well as the spaces between 
them are occupied by filaments of the fungus. The 
former are not so rapidly killed by the fungus as are 
those of the potato plant by Phytophthora infestans. 
The ultimate collapse of the plant, however, is brought 
about by the extension of the fungus to the vascular 
cylinder of the stem, and the consequent reduction of the 
supply of water to the leaves. 
In moist weather the fungus gives rise to conidia on the 
diseased stem. Unlike those of Phytophthora infestans 
they are only produced under water, and do not become 
detached from the filaments bearing them. A few hours 
after their first appearance they burst at the apex liberat- 
ing about fourteen motile spores which, after swimming 
about for a short time, come to rest and are able to infect 
other seedlings. 
in studying this disease the writer has up to the present 
failed to find any resting spores of the Phytophthora in 
the tissues of diseased asters, and attempts to obtain such 
spores by artificial cultivation have been equally unsuc- 
cessful. Experience however has shown quite conclusively 
that the disease originates each season from the presence 
of the fungus in the soil, especially of the seed bed; and 
the ease with which it may be cultivated on dead organic 
substances suggests that it may be able to persist in a 
vegetative condition in the rich soil used for seed-beds. 
On the other hand, further research may prove the exist- 
ence of resting spores. 
It is often stated that this disease is caused by a species 
of Fusarium, which is frequently found on the decaying 
