136 DISEASES OF GLASSHOUSE PLANTS 
due to Bacterium vesicatorium Doidge. Numerous dark 
green, semi-translucent, water-soaked spots appear on 
the under surface of the leaves. These increase in size, 
until they become 2 mm. in diameter, and may be either 
round or irregular in shape. They are slightly sunken 
and frequently coalesce to produce discoloured streaks. 
Finally the affected portions dry up and break away 
from the rest of the leaf. Affected leaves become 
twisted and distorted. Similar spots appear on the 
calyces, laterals, etc. Cankers are produced on the 
stems, especially the older parts, where the tissues have 
been injured by friction. These are corky in appearance, 
“ raised and roughened with numerous small, longitudinal 
cracks.”’ The disease is apparently superficial and does 
not penetrate into the wood. On the fruit a “ minute 
green or brownish blister is the first indication of 
infection.”’ Later the spots become “ hard and scabby 
in texture and usually slightly convex.” ‘‘ The epidermis 
ruptures in the centre, showing whitish-brown over the 
discoloured tissues, like the broken edges of a blister.” 
Rarely are the individual scabs more than 5 mm. in 
diameter, but by coalescence, large, scabby areas 
several centimetres in extent may be produced. The 
cracks produced in the scabs permit secondary infection, 
and a soft rot may take place. The disease is not con- 
sidered serious, but by disfiguring the fruit its market 
value is reduced. 
Tomato Fruit Diseases 
Two of these are attributable to bacteria, namely, 
a soit rot and a brown rot. 
(a) Soft Rot.—This is typically a disease of green 
tomato fruits, and usually appears towards the end of 
the season. A pale green, water-soaked spot can be 
noticed at first, which enlarges rapidly, while the tissues 
beneath collapse and the surface of the fruit becomes 
flattened. Finally the entire flesh of the tomato is 
