DISEASES DUE TO FUNGI 113 
do not bear spores, and therefore attention need be paid 
only to the wood of the previous season. 
To be effective, spraying or dusting should be con- 
ducted early in the season, before the fungus has gained 
entrance to the leaves. In America repeated dusting 
with a powder composed of 90 parts finely ground sulphur 
and 10 parts powdered arsenate of lead has proved 
effective in controlling the disease. 
Spraying with Bordeaux Mixture or lime sulphur 
(1 in 50) has also proved effective, but both these sprays 
disfigured the trees, and therefore they can only be 
employed before the blossoming period begins. 
Downy Mildew of the Sweet-pea.—This is practically 
the only important leaf disease of the sweet-pea under 
glass. It is caused by Peronospora trifoliorum De Bary. 
The disease first appears when the young plants are 
barely three inches high, but it is not uncommon to see 
older plants affected. As in the case of the rose, but 
little is seen of the causal organism, typical signs of the 
disease being the yellowing and dying of the foliage. 
The delicate fungal filaments may be seen readily, 
when diseased leaves are submitted to microscopical 
examination. Under exceptionally moist conditions, 
however, a delicate grey mould develops. Attention 
to cultural conditions constitutes the best way of con- 
trolling the disease. All diseased parts of plants should 
be at once destroyed to prevent further spreading of the 
trouble. 
(C) FRUIT DISEASES 
“ Buckeye” Rot of Tomato Fruits.——This is mainly 
a disease of the first or lowest truss of fruit of the tomato, 
but it has been found occasionally on the second, where it 
has come into contact with a diseased truss below. It is 
known by different names, such as ‘ bad-penny,”’ 
“black rot,” “ water rot’”’ or “ buckeye rot.” Affected 
8 
