Development and Cytology of the Endobiotic Phase of Physoderma Pulposum

Abstract

Lingappa, Yamuna. (U. Michigan, Ann Arbor.) Development and cytology of the endobiotic phase of Physoderma pulposum. Amer. Jour. Bot. 46(4): 233–240. Illus. 1959.—The contents of the zygotes of Physoderma pulposum pass into the epidermal cells of the host and become incipient primary turbinate organs. The latter develop into resting sporangia in 3 different ways: (1) Occasionally, they may become thick walled as sporangia in their entirety. Such monocentric development of the endobiotic thalli is described for the first time in Physoderma; (2) usually, however, the contents of primary turbinate organs undergo centripetal cleavage; or (3) their contents may be cleaved tangentially. As a result, several uni‐ or multinucleate segments are formed which give rise to tenuous hyphae. The swollen distal end of each tenuous hypha develops into a secondary turbinate organ which in turn gives rise to hyphae and tertiary turbinate organs. Thus, the polycentric organization of the rhizomycelium is maintained. During this process, buds, which develop in the axils of the apical tufts of haustoria of turbinate organs, enlarge into resting sporangia. Nuclear divisions in turbinate organs and of resting sporangial initials are mitotic, and 4 chromosomes are evident on the equator of the intranuclear spindles. As the resting sporangia are inoperculate, the endosporangia protrude through irregular openings in the exospores.