306 Gardening 
(3) Seed treatment. The aim of this method of 
disease prevention is to destroy the parasites that exist 
in some form either on or in the seeds. Soaking seed in 
hot water or in solutions of certain chemicals will often 
kill these parasites. There is, however, danger of in- 
juring the seeds, especially if they are allowed;to soak too 
long or if they are not properly dried afterward. The 
treatment most effective differs widely according to the 
kind of seed and the kind of fungus. Seed treatment is 
useless when seeds are planted in infected soil. Corrosive 
sublimate, sometimes used in seed treatment, is a deadly 
poison. Formaldehyde is extremely irritating to the 
skin and to the nose and eyes. Seed treatment should 
not be undertaken by the beginner in gardening without 
considerable study of the literature and without a spe- 
cial demonstration or study of the methods. Children 
should never attempt the work alone. 
(4) Fungicides. The use of fungicides, of which 
Bordeaux mixture has already been mentioned, has now 
become very general in combating various fungous dis- 
eases. This aims chiefly to destroy the fungus at the 
time it is gaining entrance to the leaves. The chemicals 
applied stick to the leaves after the surface becomes 
dry. When the leaves become wet from dew or rain, 
the poisons are dissolved in the films of water that 
cover the leaves. The poison is therefore present to 
destroy spores‘ which may lodge and germinate in the 
water. Sooner or later the poisons which were ap- 
plied are washed from the plant; therefore the gar- 
dener must spray repeatedly, and most often when dis- 
eases are especially destructive or the weather rainy. 
