Stages in the Development of Thelotrema Interpositum

Abstract

Thelotrema is the type genus of a family of discomycetous lichens which, though widely distributed throughout the world, occurs primarily in tropical and subtropical regions. With the exception of a few remarks by Redinger (1936), based upon work with herbarium material, no developmental study of the genus has appeared to date. Material of Thelotrema interpositum (Nyl.) Muill. Arg. was obtained near Perkinston, Stone County, Mississippi, in December, 1938, June, 1939, and August, 1940 (killed and fixed in formol-acetic-alcohol and in Navashin's solution). Permanent slides, prepared after embedding this in low-viscosity nitrocellulose by the method described by Koneff and Lyons (1937), were supplemented by smears prepared in the field. Examination of this material has enabled the writers to ascertain stages in the development of the species which seem to be of sufficient interest to justify their description and illustration at this time.