POTASSIUM CHLORIDE (MURIATE OF POTASH). 119 



On the other hand, a 6 per cent solution of kainite has no injurious 

 effect on the most tender part of the plant. 



Use. — As Pickle for Seed-Corn Smut. — G. Arieti tried to 

 disinfect seed-corn against smut by steeping it for twenty-four hours 

 in a 0"5 per cent solution. At that strength potassium sulphate 

 has no injurious action on the germination of the grain, but neither 

 is its action on the spores very pronounced. A 2 per cent solution 

 renders the spoi-es of Tilletia (bunt) inactive, but the seed already 

 suffers. G. Ville, having observed that a want of potash in the 

 soil seems to favour the development of the PJiytopJithora infestans, 

 De By. (potato disease), recommended the use of potassic manures to 

 combat it in a preventive manner. Care must be taken, however, 

 not to use larger quantities than 600 kilogrammes per hectare, say 

 528 lb. per acre, for at that dose potash salts diminish the yield in 

 starch. These salts are also employed against phanerogamic parasites, 

 such as dodder. 



Cuscuta epithipnum, Murray (dodder of trefoil and lucerne). — 

 Their sensitiveness to metallic salts is very great, and these parasites 

 may be easily destroyed by watering the fields with such solutions. 

 In the same way as the sulphates of iron and copper, green and blue 

 vitriols, which give good results, the sulphate of potash may als^ be 

 used. Yesque recommends to dust with this product in a heavy 

 morning dew the plots invaded by dodder. Next morning, after this 

 treatment, the fields of trefoil and lucerne present a lamentable appear- 

 ance ; all the plants are brown and look as if burned, but the effect of 

 sulphate of potash on leguminosae is only fleeting, and in eight days 

 these plants have resumed their vitality, whilst the dodder is destroyed 

 to such an extent that it does not reappear the following year. The 

 dose to use is from 200-250 grammes per square metre, say 7-8 

 oz. per square yard. 



Equisetum arvense, L. (meadow horse-tail). — This plant, which 

 contains aconite, is injurious to cattle. Tacke advises, to free crops 

 infested with it, to water them with a concentrated solution of 

 potassium sulphate ; the gramineae can resist this treatment, whilst 

 the horse-tails died. 



Heterodera Schachtii, '^chra. (nematode of the beet). — As a sequel 

 to Liebig's researches, concluding that potash is a necessary food of 

 this plant, it was observed that potash salts used in beet growing, up 

 to a certain dose, remedied the exhaustion of the soil. Kuhn sided with 

 the general opinion that such salts acted by their nutritive properties 

 and replaced the potash removed by the beet. Webster and Hopkins 

 still hold this opinion and deny the insecticide action of potash salts. 

 But after it was found that the exhaustion of the land by this crop 

 was due in great part to an excessive growth of small worms, 

 nematodes, Hollrung tried the action of potash salts on their larvae. 

 He remarked that the latter, more sensitive than the adults, died in 

 forty-eight hours in a 1 per cent solution of potassium chloride and in 

 three hours in a 5 per cent solution. Potassium sulphate is less 

 active in a 1 per cent solution as it takes ninety-six hours' immersion 

 to destroy the larvae, and has the same toxicity as potassium chloride in 



