ULTRASTRUCTURE OF BASIDIOSPORES IN NORTH-AMERICAN MEMBERS OF THE GENUS CALVATIA

The scanning electron microscope was used for a comparative study of b asidiospore morphology in the genus Calvaria. Basidiospores of the spe cies C. pachyderma, C. fumosa, C. sculpta, C. subcretacea, C. gigantea , C. booniana, C. tatrensis, C. depressa, C. craniiformis, C. rubrofla va, C. elata, C. cyathiformis, and C. bovista were compared to determi ne whether the stirp groupings described by Zeller and Smith (1964) ex tend to spore ornamentation. The surface ornamentation of Calvatia spo res examined is generally verrucose/echinulate with the exception of C . pachyderma which is completely smooth. Correspondence between our da ta on spore ornamentation and Zeller and Smith's stirpes groupings bas ed on gross morphology was found in C. craniiformis and C. rubroflava as well as in C. booniana and C. gigantea. Our results show spore orna mentation, a highly conserved characteristic, can be used to clearly d istinguish these species in the genus Calvatia and should be used in a ddition to gross morphology of the sporocarp when classifying them.