130 VEGETABLE FORCING 
In this connection it is stated, in the Market Growers’ 
Journal, that by merely watering bed surfaces with a hose, 
little moisture reaches the foliage, and thus the bordeaux 
mixture does not become effective. To the writer the 
explanation lies in the need of atmospheric moisture to 
make the copper compounds soluble in bordeaux mixture. 
Wherever, therefore, there is in greenhouse practice no 
moistening of the foliage, bordeaux mixture will not 
become available for fungicidal effect to any considerable 
extent. 
It is important, therefore, to maintain a supply of soil 
moisture sufficient to cause normal growth. It also seems 
that inadequate soil moisture, which may cause a slow, 
weak growth, makes the plant more susceptible to cer- 
tain diseases. 
The influence of temperature.—Very high temperature 
in the greenhouse may render the plants susceptible to 
disease. No harm will result from high temperature if 
there is sunshine, normal soil moisture conditions and 
proper ventilation. But excessive heat and high humidity 
in the absence of sunshine are certain to cause very rapid 
growth and soft, tender tissues which are most sensitive 
to diseases. High temperatures and abundant moisture 
also provide the most favorable conditions for the germi- 
nation of spores and the further progress of diseases. 
Great extremes in temperature should be avoided because 
they are not conducive to the strongest growth of the 
plant. 
Vigor of growth.—It is universally conceded that 
greenhouse plants which are making a normal, vigorous 
growth are the least susceptible to disease. It behooves 
the grower, then, to maintain soil and atmospheric condi- 
tions which are most favorable to the plants under culti- 
vation. This involves careful and intelligent fertilizing, 
watering and ventilating. There must be no neglect in 
firing the boilers or in any other operation that is essential 
to the growth of disease-resistant plants. 
