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. 



