Studies on the Morphology and Development of an Insect-Destroying Fungus, Entomophthora Sphaerosperma

Summary

1.	Cultivation of Entomophthora sphaerosperma on artificial media has made a detailed study of this entomogenous fungus possible.
2.	The single spores are true conidia, in that they are not formed within a separable sporangium.
3.	The forcible projection of the conidium from the conidiophores is due to a definite chain of occurrences, chief among which are swelling of the conidiophore, circumferential rupture of the attachment around its tip, and a recoil of the spore's basal membrane.
4.	The conidium possesses a gelatinous apical cap, which aids in its attachment to the host.
5.	Conditions most favorable for spore germination are a temperature of 20° C., a relative humidity of 70 per cent or more, and darkness. Conidia are not injured by freezing.
6.	Rhizoids are not formed in artificial culture; all other phases of the life cycle are the same in artificial culture as in the insect host.
7.	During mitosis, the nuclear membrane persists until the telophase. Definite chromosomes, at least twelve in number, are formed. A well-defined spindle exists and one or more nucleoli are present throughout division, distinct from the chromosomes.
8.	Resting spores in this species are formed asexually and are therefore azygospores. Their formation is subject to artificial control in which the determining factors may be either temperature or special artificial media.