The White Form of Physarella Oblonga

Abstract

Physarella oblonga (Berk. & Curt.) Morgan, the only species in the genus Physarella of the Myxomycetes, is easily distinguished from any other slime mold by its unique thimble-shaped sporangia and the spinelike processes of the capillitium which extend out and stud the surface of the peridium. The organism is of world wide occurrence, Martin (8) describing its distribution as Throughout North America, Cosmopolitan. All monographers are in general agreement concerning the color of the stalk, the peridium, the capillitial knots, and the plasmodium. The peridium is described by Lister (6) as a yellow membrane thickened with deposits of yellow-lime granules and studded with the spine like processes of the capillitium; by Macbride and Martin (7) as tawny, roughened by numerous yellowish, calcareous scales . . . ; by Hagelstein (5) as a yellow stout membrane, thickened with yellow limegranules; and by Martin (8) as greenish with shadings of brown or red, flecked with yellowish scales. The same authors describe the stalk as red-brown or red; the lime knots of the capillitium as yellow or orange; and the plasmodium as rich yellow or yellow. Cultural studies by Abbott (1), Gray (4), and by Gehenio and Luyet (3) indicate that the organism grows well in crude culture and that it is homothallic since monospore and monamoebal cultures produce plasmodia and eventually fruiting bodies, and since Ross (9) has established that plasmogamy takes place in this organism and results in the formation of zygotes. In the fall of 1962 two-membered cultures of Physarella oblonga with Aerobacter aerogenes were established in the laboratory as were axenic cultures of plasmodia, purified by the migration process, which are being maintained on oat flake agar (unpublished research).