eM ae | 
DISEASES DUE TO FUNGI 89 
suitable conditions for the growth of fungus repro- 
ductive bodies which may settle there. All diseased 
plants should be removed and burned, for if they are 
allowed to lie and decay in a heap or on the ground the 
sclerotia will fall out of the stems into the soil. In the 
following spring the sclerotia give rise to several brown 
funnel-shaped structures with long slender stems. These 
ascophores, as they are called, produce innumerable 
spores, which if carried by the wind to a susceptible host 
plant will cause disease. The cucumber is more suscep- 
tible to this disease than is the tomato, and in the case 
of the latter crop a virulent outbreak is a sign that some- 
thing is wrong with the physical factors in the plant’s 
environment. In bad cases sterilization of the soil will 
destroy the disease organisms, but generally it is sufficient 
to water the soil with a solution of “ Cheshunt Com- 
pound ”’ before planting. When the disease appears the 
base of the affected plants should be watered with this 
solution, as also should the neighbouring healthy plants. 
Stem “‘ Canker” of the Tomato.—This disease became 
of serious importance to the tomato industry during the 
early part of the present century. It was at first attri- 
buted to a fungus, Mycospherella citrullina Grossenb., 
described as the cause of a stem disease of the melon in 
America. Brooks and Searle have recently shown that 
the fungus was incorrectly identified and is really Diplo- 
dina lycopersici Cooke, Holtos emend., Brooks and 
Searle (13). 
About 1909 the disease had reached its maximum 
virulence, and was extremely dangerous, but since then 
it has decreased in power, until at the present time it 
exists only in isolated places. Attention is first drawn 
to the disease by the wilting of the affected plant. 
Examination of the base, where the fungus infection 
commences, shows the tissues to be waterlogged and pale 
in colour. Later the affected portions become grey and 
finally black. The diseased stem becomes shrunken, 
