124 JOURNAL OF THE 



in some experimeDts conducted by him under the direction 

 of Dr. Riley, has shown that the application of bisulphide of 

 carbon, kerosene emulsion and various arsenical solutions, in 

 Cjuantities sufficient for the destruction of the worms, was gener- 

 ally fatal to the plants themselves, while the use of alkaline 

 fertilizers, like hard-wood ashes, muriate and sulphate of potash, 

 kainite, etc., produced a hard growth less susceptible to attack. 



Sterilization of the Soil by Starvation. — The cheap- 

 est and probably at the same time the most effectual mode of 

 sterilizing the soil will be to starve out the worms by a rotating 

 system applied to the selection of fields or plats of ground u])on 

 which are grown only such plants as are positively known to be 

 insusceptible to attack. A real difficulty arises even here, for 

 so many plants in widely different families are known to be sus- 

 ceptible to the disease, and plants that are absolutely insuscepti- 

 ble can in some cases only be determined after a series of trials. 

 Dr. Neal reports {loc. cit.) that according to his experience Ama- 

 rantus spinosus is the "most dreaded and destructive agent in 

 the spread of the root-knot." In this section, even in the imme- 

 diate neighborhood of other plants badly diseased, I have found 

 this species free, so far as examined, while Amayxintus retroffexus 

 growing side by side with it is diseased. Similar cases in the 

 habit of a related species of Hetcrodera {H. Schachtii Schmidt) 

 are reported from Europe. This species is very destructive to 

 sugar-beets and many other plants. Among a number of plants 

 which were supposed to be insusceptible was barley.* Upon a 

 piece of land very badly infected by the '^Riibennematode" bar- 

 ley was sown for three years successively. The first two years 

 no injury was noticed, but in the third year the crop was destroyed 

 a short time before harvest by severe attacks of the worms. Dr. 

 Neal {loc. cit.) also speaks of the Japan Clover [Lespedeza striata) 

 as a substitute for the cow-pea [Dolichos catiang) as a forage 

 plant and fertilizer. In tiiis vicinity Lespcdeza striata ranks as 

 one of the species slightly affected, while "bird\s-foot clover'^ 

 [Lotus corniculatus) is very badly affected. It is evident that 



*Quoted from Sorauer, Pflanzenkrankheiten, Zvveite Auflage, Vol. II, p. 853. 



