Occurrence of Scirpus georgianus (Cyperaceae) in Maine.

摘要

Scirpus georgianus R. M. Harper is a perennial, grass-like herb of wetland communities. It is closely related to S. atrovirens Willd., and the two are part of a group of five morphologically similar species in North America [e.g., S. atrovirens, S. fiaccidifolius (Fernald) Schuyler, S. georgianus, S. hattorianus Makino, and S. pallidus (Britton) Fernald]. The S. atrovirens complex is recognized by: trifid styles; mucronate scale apices; relatively straight perianth bristles with thin-walled, round4ipped retrorse barbules confined to the distal lA of the bristle; and a haploid chromosome number of n = 25-28 (Schuyler 1967; Schuyler and Whittemore, in press). Identification of Scirpus georgianus relies primarily on perianth bristle morphology. This species frequently lacks bristles altogether. When bristles are present, they number 1-3 per flower, are typically very short (rarely up to 0.75 times the length of the achene), and are smooth or have a few retrorsely oriented barbules near the very tip of the bristle. All other species of the S. atrovirens complex have 5 or 6 perianth bristles that are usually more than 0.75 times as long as the achene and are retrorsely barbellate in the distal lA or more of the bristle. Further, the haploid chromosome numbers of S. georgianus (n = 25, 26, and 27) are relatively unique in this complex (Schuyler and Whittemore, in press). Only the n = 27 cytotype is shared with another species--S, fiaccidifolius of the mid-Atlantic and southeastern United States.