DISEASES DUE TO FUNGI 65 
fungi found on vegetation. The fertile hyphz stand up 
in dense grey, velvety tufts and masses, producing oval 
conidia or spores on branched heads. These conidia are 
extremely light, and, being carried long distances in 
strong air currents, provide a most efficient method of 
spreading the disease. Numerous hard, black sclerotia 
are produced on the plant, and being highly resistant to 
abnormal conditions enable the fungus to hibernate from 
one season to the next. 
Sources of Infec- 
tion.—The infection is 
present at the surface 
of the soil, and may 
have been introduced 
by air currents, or 
with water supply, or 
manure, 
Control.—Warm, 
moist conditions at 
the base of the plant 
favour this disease and 
therefore should be 
avoided. Oncea plant 
is attacked nothing 
can save it, but the 
fungal infection present 
at the soil surface and 
plant base may be de- 
stroyed by spraying Fig. 10. Macrosporium foot rot of the tomato: 
with a 9 per cent solu- (a) spores, (b) diseased stem. 5 
tion of calcium bisulphite, which is specific for Botrytis. 
Macrosporium Foot Rot.—Quite recently Rosenbaum 
(42) has described a foot rot of the tomato due to 
Macrosporium solani E and M. 
Symptoms.—The symptoms are described as resem- 
bling those of black-leg of potato stems. The stems 
turn dark brown at the ground line, and the tissues 
5 
