84 



INSECTICIDES, FUNGICIDES, AND WEED KILLERS. 



(2| bushels) in 22 gallons of 0-5 per cent acid, and sowed immediately 

 afterwards. This method has since been tested by specialists of high 

 reputation and found deficient. Kuhn has shown that not only was the 

 0"5 per cent acid an anodyne for the spores, but had the drawback of 

 being more injurious than sulphate of copper. The injurious action 

 of the acid on cereal grains does not make itself felt for some time. 

 Such seed-corn always retaining a little sulphuric acid cannot dry up 

 completely and rot. This drawback may be avoided if care be taken 

 to wash the seed in milk of lime immediately aftei- steeping in the 

 acid. In fact, Boiret found that the spores of bunt were not com- 

 pletely destroyed after a twenty-four hours' steep in a 5 per cent acid, 

 and that a 20 per cent acid destroys the grains of wheat without killing 

 the germs of the disease, even if steeped six hours therein. All cereal 

 grains are thus sensitive to the action of HoSO^ ; however, amongst 

 the different species of wheat there are some which stand the acid 

 better than others. 



TABLE XL — Effect of Steeping Seed Wheat for Different Lengths of Time in 

 Dilute Sulphtiric Acid on Germinative Capacity per cent. 



It follows that this acid does not possess the requisite properties to 

 replace blue vitriol in the pickling of seed corn. The only seeds that 

 can stand steeping in the acid are beet-seeds, which are surrounded 

 by a protecting sheath which enables them to stand steeping in acid 

 of 66° Be. (168° Tw.) without their germinative capacity being dimin- 

 ished. This protecting sheath acts as a shelter to the germs of fungi 

 and bacteria of the most diverse nature, such as PJiotna tabifica, Prill. 

 et Delacr. ; Pythmm de Baryanum, Hesse ; Bacillus myco'ides, Bacillus 

 butyricus, Proteus vulgaris. As soon as the radicle and cotyledons 

 of the beet appear these fungi invade them, disturb the normal evolu- 

 tion and induce rot. Hiltner found that the 30°-35° Be. acid will 

 destroy the germs of all these parasites. Linhart recommends 66° Be. 

 (168° Tw.) acid in which the seed is steeped half an hour, then 

 washed ten minutes' with a jet of water, then the seeds are dipped 

 into milk of hme, and all that now remains to be done is to wash the 

 seed for four hours in running water. The seeds so treated are in no 

 wise injured. Their germinative capacity is increased ; they spring up 

 more rapidly and in larger quantity, and the disease germs are com- 

 pletely destroyed. For reference purposes a description is here given 

 of the researches published on the resistance of spores of different 

 fungi to dilute H2SO4. These laboratory trials were made by incor- 



