Abstract
In several previous publications by the present writer reference has been made to the relation between the root excretions of plants and the bionomics of the eelworm Heterodera schachtii. Amongst these is a short preliminary note on the significance of the root excretions of certain grasses as a possible means of controlling the nematode. The experiments referred to in this paper having been continued and extended, and the favourable results of the first year's field work having been maintained, a more detailed account of the researches seems to be justified, although the field experiments are still in progress and many aspects of the problem which require laboratory investigation are as yet comparatively untouched. As previously indicated, of the two main lines, chemical and biological, along which investigations must be pursued for a full understanding of the relationship between the reactions of the nematode and the stimulus of the root excretions, the chemical is the more fundamental, and until further work has been carried out from this standpoint much of the biological work is necessarily of an empirical character. It is, however, on purely biological lines that the greatest progress has so far been achieved, and it is with this side of the work solely that the present paper deals.