A life cycle of Blastocladia pringsheimii reinsch

Abstract

Summary Although Blastocladia Pringsheimii has been known much longer than any species of Allomyces and Blastocladiella , its life-history has so far eluded discovery. This is partly due to the difficulty of inducing the resistant sporangia to germinate in culture. A description of the mature resistant sporangium is given, especially of the structure of the thickened, pitted wall. Resistant sporangia have now been successfully germinated on many occasions by ensuring first that they were fully mature. Practical hints arc given for the encouragement and control of germination. Phenomena of germination are described and illustrated: the cracking of the thick wall, the development of a papilla, the formation and emission of swarmers. The fate of the swarmer is followed and its direct germination into a germling of characteristic form is described. Germlings have been cultivated ( a ) on tomatoes in water, ( b ) in slide cultures, ( c ) on agar plates, and the mature thalli formed in these three types of culture shown to be quite different in form but always to liberate swarmers which have not fused but have germinated directly into groups of plants—the characteristic “pustule”. The life cycle here described corresponds with the short cycle of Emerson's sub-genus Brachyallomyces and Matthews's Blastocladiella simplex . It is not suggested that another type of life cycle is impossible. Blastocladia Pringsheimii has shown itself to be of so variable a form both in nature and in culture, that it may well be variable also in its life cycle. It is my pleasant duty to acknowledge the useful criticism and practical help generously given by Miss Grace Waterhouse and Dr Ralph Emerson towards the close of this investigation, and to thank Mrs Edmund Mason for kind help with the drawings.