Scopelophila cataractae in Texas

Abstract

Scopelophila cataractae (Mitt.) Broth. is reported for the first time from Texas on a collection from an igneous substrate in Brewster Co., in Big Bend National Park. Small gemmae are borne on branching, green, protonema-like filaments in leaf axils of the Texas plants. Locality records in the United States of Scopelophila cataractae (Mitt.) Broth., a rare copper moss, include Arizona, California, North Carolina, Pennsylvania, and Tennessee (Shaw & Beer 1989). Copper mosses are noted for growing on substrates enriched with metals. The present collection is sterile, as are all others from North America (Shaw & Beer 1989). TEXAS. BREWSTER CO.: Big Bend National Park, Burro Mesa, in Apache Canyon near its head, ca. 29*17'N, 103*25'W, on moist igneous detritus and in seepage cracks below intermittent waterfall, Reese 17344 (BUF, DUKE, LAF, MICH, MO, NY, US). Burro Mesa is largely composed of volcanic material, including lava and ash beds (Maxwell 1968). The general area of the collection site is composed of soft, tuff-like strata with brilliant hues varied from reddish through yellow-orange to violet, perhaps indicative of mineral enrichment. Apache Canyon is relatively remote from human influences today, although it was apparently heavily used by Indians (based on abundant artifactual evidence in the vicinity) and, more recently, by cattle ranchers (Maxwell 1968). Mercury (cinnabar-HgS) mines and smelters-no longer operating-are located in Brewster Co., including one in the Park itself, but there has never been mining activity at Apache Canyon. The nearest mercury mine site is at Study Butte, ca. 11.5 km NW of Apache Canyon. Thus the Apache Canyon population of S. cataractae is growing on a presumably metal-rich subtrate that has not been modified by human activity, as is the case for some locales for this moss. Although protonemal gemmae have apparently not been reported for American material of S. cataractae, they have been reported for this moss from other parts of the world (reviewed by Arts 1988, with illustrations). What may be termed protonemal gemmae (Fig. 1) are produced sparingly on ascending, green, branching, protonema-like structures in leaf axils of the Texas plants; they readily dehisce from the filaments that bear them. The minute gemmae, to ca. 14.5 x 60 #Am, are composed of 1-3 cells in linear arrangement, and have thick walls and dense contents. Some of the larger gemmae are FIGURE 1. Outlines of protonemal gemmae of Scopelophila cataractae (Mitt.) Broth., one still attached to protonemal filament; all from Reese 17344. Scale bar = 50