CELLULOSE AS A SUBSTRATUM FOR SAPROPHYTIC CHYTRIDS

Abstract

SINCE APRIL, 1938, collections of saprophytic chytrids have been made from bait placed in ponds near the Thames River on the campus and in a sphagnum bog at North Bay, Ontario. The method of baiting was that used by Karling (1935). A number of these chytrids are being kept in culture. In general, methods and technique followed are those described recently by Couch (1939) and brought here by Miss Berdan from his Chapel Hill laboratory after the summer of 1938. All cultures have been kept under as nearly sterile conditions as possible in a room with controlled temperature (about 60?F.). Until January 30,1939,the substrata used were leaves of wheat, corn, rye, oats, other cereal grains, and grasses from which the chlorophyll had been removed. There are some practical disadvantages in their use. One is the necessity of keeping the plants in young stages all year in the greenhouse. Secondly, the thickness of the leaves, the presence of stomata, the epidermal hairs, and even the cell walls often tend to obscure the early stages of growth from the germinating zoospores. Very young, thin leaves are used to offset this, but their tissues break down rapidly, and the cultures require constant care. Even with older leaves, some chytrid species develop so rapidly that water and substratum have to be changed every few days. When several hundred cultures are being kept over long periods, the labor and inconvenience are excessive. During a conversation in January, 1939, Dr. F. K. Sparrow, Jr., suggested the use of paraffined filter paper as a substratum, following Dr. Rex Webster (Middlebury College, Vermont), who had grown a species of Rhizidiomyces2 upon it. More than fifty years ago, according to Schr6ter (1889), Rhizophlyctis rosea (de Bary and Woronin) Fischer was found on moist blotting paper by Sorauer in Germany. OBSERVATIONs.-It had been noticed in our laboratory that most of our forms seemed to thrive equally well in leaves lacking nearly all cell contents as in those (e.g., young wheat) with globules of brown oil. Consequently, lens paper (Cenco) in which the individual fibers could be distinguished under the microscope was substituted for paraffined filter paper. On January 30 a small rectangle of this was added to a healthy culture of Rhizophlyctis