62 



EFFECTS OF MOISTURE AND LIGHT 



A certain degree of moisture is evidently essential to nematodes 

 and they do not appear to suffer much from an excess of it, as we 

 have kept them in watery sohitions for days at a time with no detri- 

 mental results. While nematodes naturally prefer the dark, as does 

 their relative the earth worm, their exposure to light, as far as we 

 have observed, causes no appreciable harm and they appear to mul- 

 tiply and thrive as well in it as they do in darkness. 



EFFECTS OF ELECTRICITY. 



Some experiments were made with nematode infested earth with 

 alternating electric currents of varying strengths. The infested 

 earth was placed in a glass tube | in. in diameter and the various 

 samples were subjected to different strengths of an alternating cur- 

 rent for a period of one minute each. It is sufficient to say that the 

 experiments proved of very little value, but they indicated that the 

 amount of current necessary to rid the soil of nematodes would have 

 to be large enough to produce considerable heat in the soil and at 

 the present time there is no indication that this method of treatment 

 would be practicable. We have demonstrated by experiments in our 

 laboratory that the amount of alternating current which seeds can 

 stand without being destroyed is largely determined by the amount 

 of heat they are capable of enduring and in all probability the same 

 would hold true of nematodes. There is reason to believe, however, 

 that this statement would not hold good for direct currents. A cur- 

 rent sufficiently strong to produce electrolysis in an organism would 

 probably cause disintegration and death to nematodes. 



EFFECTS OF DESICCATION. 



Neither nematodes nor their eggs can stand desiccation. Jars 

 containing innumerable nematodes were allowed to dry at the tem- 

 perature of the laboratory and when examined one year afterwards, 

 after having previously been moistened with sterilized water for some 

 weeks, showed no evidence of nematodes. The same results have 

 been obtained when we allowed nematode infested earth and other 

 infested material to become dry. It is hoped that some practical use 

 can be made of this fact in treating nematodes in greenhouses. 



