Basidiospore Wall Ultrastructure and Tissue System Morphology in the Genus Calostoma in North America

Abstract

The three North American species of Calostoma and one variety were studied from both fresh and dried material. Spores were examined using light microscopy as well as scanning and transmission electron microscopy. The structure of the spore wall is described for the first time for the three species. Tissue systems in the sporocarps were studied from immature and mature specimens using light microscopy. New information is presented on the arrange- ment of the tissue systems and the structure of the walls. Complete descriptions of each species are presented and accompanied by information on their known distribution in eastern Calostoma is a monotypic genus in the Calostomataceae (Gasteromycetes, Tulostomatales) (Dring, 1973). The generic concept is based on C. cinnabarina Desv. (1809). Members of the genus are distributed worldwide in regions of de- ciduous, temperate, tropical or subtropical forests in Indonesia (Borneo, Java, Sumatra, New Guinea), Ceylon, Himalaya, Nepal, Taiwan, China, Australia, New Zealand, North America, and Latin America. Of the ten to sixteen recog- nized species (Dring, 1973; Guzman, 1973), three occur in the western hemi- sphere: Calostoma cinnabarina Desv., C. lutescens (Schw.) Burnap, and C. ravenelii (Berk.) Massee. All three occur in the eastern and southeastern United States and Mexico, and C. cinnabarina occurs in Columbia. The species included within the Calostomataceae are typified by Dring (1973) as having a complex peridium of four clearly defined layers, the outermost ge- latinous or spiny, the second pigmented, the third very horny, the innermost membranous and remaining attached to the outer layers only at the top of the star-shaped apical pore. The gleba is pale, with initially thickened capillitium which disintegrates at maturity. Primary infertile basidia form small islands which are surrounded by secondarily fertile, pleurosporous basidia. Spores are large and ornamented either with a reticulum or long spines. Clamp connections are present. The morphology of the tissue systems of Calostoma species has not been adequately described. Likewise the spores of the genus have been only superfi- cially examined although the genus has been the subject of several monographs and regional reviews (Massee, 1888; Burnap, 1897; Webster, 1899; Boedijn, 1938; Guzman, 1973; Chen and Yeh, 1975). The family has also been placed within the Sclerodermatales by Zeller (1949). There are conflicting descriptions of the spores and tissue systems studied with light microscopy. Light microscopy is therefore inadequate for complete and accurate characterization of spore ultrastructure and morphology. We have used scanning and transmission electron microscopy (SEM