Despite difficulties in taxonomic circumscription and phylogenetic placement, the Calymperaceae, a diverse and ecologically important family of tropical mosses, exhibits an array of peculiar features. The ‘leucobryoid’ leaf architecture, found in some members of the family, features distinctive layers of chlorocysts and hyalocysts. Edwards (1980, J. Bryol. 11:49-93) previously studied layers of the resorption pores in the hyalocysts in the more "normal" leaves of Calymperes. As part of ongoing phylogenetic and monographic research in the Calymperaceae, we observed microscopically the variation of resorption pores among exemplar members of the family and its putative relatives, and evaluated their potential as taxonomic characters. Internal pores of hyalocysts are distributed on the lateral and transverse walls whereas pores on the adaxial and abaxial walls (when present) are open to the exterior. This investigation supports recent phylogenetic analyses indicating an expanded concept of the Calymperaceae and helps to resolve relationships within the family. Acknowledgment: We are grateful to acknowledge the funding provided by the National Science Foundation (PEET: Partnerships for Enhancing Expertise in Taxonomy; DEB-9712347).

Key words: anatomy, mosses, phylogenetics, phylogeny, systematics