68 DISEASES OF GLASSHOUSE PLANTS 
base are the indirect cause of many root diseases. The 
soil temperature is also important, and fungi which at 
one temperature do little damage may rapidly destroy 
the whole root system at a suitable temperature. 
Tomato Root Rots.—Phytophthora cryptogea, Phytoph- 
thora parasitica, and Rhizoctonia solani, as already 
described, may produce a rapid root rot of the tomato. 
Other root rots are due to various species of Fusarium | 
and Sclerotiwm. 
Fusarium Root Rot of the Tomato.—Various species of 
Fusarium have been isolated from tomato roots in 
England, and have been found invariably to follow 
wounding by woodlice or wireworm. The fungus causes 
a reddish-brown discoloration of the roots, which spreads 
rapidly during the summer months when the soil tempera- 
ture is high. The affected plant becomes stunted in 
growth, the leaves turn yellow and wither, and finally 
death ensues. When the plant is dead the fungus grows 
out over the surface of the tissues and, unless the dead 
plant is removed in time, produces an abundance of 
spores, which rapidly spread the disease. 
Sclerotewum Root Rot of the Tomato.—In America 
Sclerotium rolfsit Sacc. has been described as producing 
a root rot of the tomato (23), but this disease is as yet 
unknown in England. Infection takes place at the 
base of the plant in about the top inch of soil, and 
becomes evident as dark brown lesions, at which stage 
the plant wilts slightly. Later the lesions become covered 
with a mat of white radiating hyphe, which surrounds 
the base of the plant. The fungus works into the stem 
tissues and the plant wilts and dies. The fungus does 
not pass up the stem to any height, but works down 
into the roots, especially those near the “surface. On 
pulling up a dead plant the roots are seen to be covered 
