Three isolates of Helicobasidium purpurem were shown, as originally isolated, to use both ammonium and nitrate N, as well as a mixture of amino acids. Two required thiamin and were partially deficient for some other growth factor or factors. The third behaved anomalouslyand its growth factor requirements were not determined. A cytological examination showed the vegetative mycelium of the isolates studied to be binucleate. H. purpureum was shown to depend on a food base for growth through soil, which was little affected by a wide range of soil conditions. The fungus showed an affinity for continuous surfaces in soil. Pieces of carrot root stimulated growth once the fungus had made contact with them, but not otherwise. Formation of mycelial strands from a food base appeared to constitute the normal growth habit of the mycelium in soil. A morphological study of strand development in natural (i.e. unsterilized) soil suggested that, under these conditions, there is some mutual attraction between the outgrowing hyphae of H. purpureum , so that hyphae coming together by chance tend to continue parallel growth in association. The coherence of strands formed in this way was increased by an interweaving growth of the main hyphae, by a binding action of short side branches and by anastomoses. The postulated attraction between hyphae presumed responsible for stranding did not, however, prevent branching of strands or their occasional disintegration into the constituent individual hyphae. Attempts to induce the formation of mycelial strands in pure culture were unsuccessful, so that it has not been possible to determine the nature of the stimulus responsible for stranding that operates upon hyphae growing through soil from a food base. Survival of sclerotia of H. purpureum was poor in an acid soil, but was unaffected by a wide range of conditions in a slightly alkaline soil. Survival in the first mixed with sand was improved when this soil was rendered alkaline. Decreased longevity of sclerotia in the acid soil was associated with a high incidence of spontaneous germination.