42 DISEASES OF GLASSHOUSE PLANTS 
are grown, serves to illustrate the intimate relation 
between plant disorders and an insufficiency of soil 
water. The first sign of the disease is the appearance 
of a small, bruised, water-soaked spot near the blossom 
end of the fruit. The spot rapidly increases in size, 
turns a brownish-black colour, and becomes hard and 
leathery. The discoloured area extends deep into the 
fruit, the affected tissue shrinks, and the fruit flattens. 
Occasionally saprophytic organisms enter the affected 
region and complicate matters by inducing a soft 
rot. Careful investigations have shown that soil 
moisture conditions affect the development of this 
disease. 
Many cases of this disease have come within the 
author’s experience, and drought has been an important 
factor in each of them. Perhaps the most striking is 
that of a nursery situated at the top of a hill where 
the only water obtainable was pumped by means of a 
gas engine. Three times within one year the engine 
broke down and no water was available for a week. 
The plants wilted badly during the day, but recovered 
at night, and from 25 to 30 days after each breakdown 
“‘blossom-end rot” appeared on the plants on trusses 
at the same level. Five tons of diseased tomatoes were 
gathered from 34,000 plants during the three outbreaks, 
but during the rest of the season, when water was given 
at the rate of 35,000 gallons per acre per week, no disease 
appeared. Plants growing rapidly and producing soft, 
sappy shoots are most susceptible to a check caused by 
drought, and are therefore more susceptible to the disease. 
Heavy dressings of stable manure and ammonium com- 
pounds favour the progress of the disease, while nitrate 
of soda and lime appear to check it. 
A disease of glasshouse plants which is the result of 
a number of different factors is that termed ‘“ Dropsy ” 
or “‘(@idema.” In this country it occurs mainly on the 
tomato and geranium, and in the case of the former is 
distinguished by a whitening or yellowing of the leaf 
