SYSTEMATICS OF THE TRIBE ORCUTTIEAE (GRAMINEAE) AND THE DESCRIPTION OF A NEW SEGREGATE GENUS,TUCTORIA

The two genera Neostapfia and Orcuttia, recognized as being closely allied and sharing unusual features, are treated as the sole members of the tribe Orcuttieae. Neostapfia is monotypic; Orcuttia comprises eight taxa, six of which are universally treated as species, and two as varieties. Studies reported here are based on field work throughout the ranges of these two genera and examination of 550 herbarium specimens. Chromosome counts and seed protein analyses for all taxa are presented. These data indicate that each taxon is worthy of specific status and that Orcuttia, as traditionally treated, consists of discordant elements. It is concluded that a more satisfactory taxonomy results when this group is split into two genera. A new genus, Tuctoria, is described, and the combinations T. fragilis (Swallen) J. Reeder, T. greenei (Vasey) J. Reeder, and T. mucronata (Crampton) J. Reeder are proposed.