DISEASES DUE TO FUNGI 69 
with a white fungal growth. If a diseased plant in the 
soil is kept under moist conditions the fungus grows out 
from the stem and spreads over the soil surface in 
radiating fans. The disease is carried from season to 
season by sclerotia as small as the smallest mustard seed. 
At first they are milk white in colour, but on maturing 
they turn a dark mahogany-red or black colour. Sclerotia 
are not produced on the plant until the final stages of 
the disease, and on dead plants may usually be found 
in abundance. Rolfs, who first discovered the disease, 
reports that it also attacks potatoes, cabbages, beets, 
and melons, as well as Hydrangeas and Daphnes. 
Control.—The disease grows rapidly in compost heaps, 
and indeed in any soil rich in decaying vegetable matter. 
Clean methods of culture and the omission of stable 
manure from the soil will prevent the disease, while 
efficient ventilation at the base of the plant and deep 
cultivation are also beneficial. Spraying the soil surface 
and base of the stem with a solution of “ Cheshunt 
Compound” is recommended as a preventative. 
Colletotrichwm Root Disease.—This disease has recently 
been identified in England. The symptoms of the disease 
are similar to those generally present when tomato roots 
are slowly destroyed by a parasitic organism. Such 
plants cease to develop normally, the lower leaves turn 
yellow and wither prematurely, and the new growth is 
thin and pale in colour. In many cases the stem becomes 
hollow and the plant dies prematurely, being relatively 
stunted in growth. 
On pulling up a plant the roots offer no resistance, 
for they are dry and shrivelled, and the decayed base 
readily leaves the soil. The cortical tissues of the 
roots readily come away from the centre core of wood, 
and the distinctive feature of the disease is the presence 
of innumerable minute sclerotia the size of begonia 
seeds (Fig. 11). These are produced inside the woody 
tissues as well as external to them. The affected wood 
