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104 DISEASES OF GLASSHOUSE PLANTS 
leaflets gradually droop and dry on the stalk, which later 
also shrivels up but remains attached to the stem until 
broken off by a slight jar. On tomatoes which are staked 
the disease is sometimes confined to the lower leaves. 
Where the plants are allowed to trail at will the disease 
may cause almost complete defoliation of the plant, the 
small tufts of young terminal leaves alone escaping. 
““'The disease is commonly found on the stems. It is 
manifested by small, slightly elongated, dark spots con- 
taining pycnidia. These spots are not so clearly defined 
as those on the leaf. The damage to the stem is slight ; 
these spots do not enlarge to form cankers and are not 
serious except in so far as they produce spores for further 
infection. 
“Small spots, more or less elongated, occur on the 
calyx, and take a form intermediate between those on 
the leaves and stems.” 
It may be remarked that the difference in form of the 
spot are doubtless due to the texture of the host. 
A moist atmosphere and temperatures of 25° C. to 
30° C. are favourable to the disease. The fungus will not 
grow at a temperature of 374° C., and ten days’ exposure 
to this temperature has been found to prevent any further 
growth even when the temperature has been reduced to 
the optimum. Control measures recommended include 
efficient ventilation, spraying with Bordeaux Mixture, 
and the enforcement of strict sanitary conditions. 
Carnation Rust.—This disease, which is probably one 
of the commonest diseases of the carnation, is caused by 
a fungus, Uromyces caryophyllinus (Schrank) Wint., and 
has been known in Europe for more than a century. 
Rust is easily recognized by the blisters or sori which are 
produced on the leaves and stem (Fig. 27). These are 
at first covered by the epidermis of the leaf, but this is 
eventually ruptured, and masses of brown spores are 
exposed. The disease begins at the lowest leaves, but 
under favourable conditions it spreads rapidly over the 
