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SUMMARY
Comparative study of several taxa classified in Helicostylum suggests that the genus is comprised of species having different relationships. Accordingly, two genera are recognized. Helicostylum Corda is reserved for those species having a sporangium without an apophysis, forming globose sporangiola borne on straight or recurved branches, and lacking stolons and rhizoids. Three species are recognized: H. elegans Corda, H. pulchrum (Preuss) Pidopl. & Milko, and H. cordense Mehrotra & Mehrotra. Helicostylum venustellum Lythgoe is relegated to synonymy with H. elegans. Thamnostylum von Arx & Upadhyay includes those species having stolons and rhizoids, apophysate sporangia, and pyriform sporangiola borne on circinate stalks. This genus also includes three species: T. piriforme (Bain.) von Arx & Upadhyay, T. lucknowense (Rai et al.) von Arx & Upadhyay, and T. repens (van Tiegh.) Upadhyay.