Abstract
Two collections referable to Orthotrichum truncato-dentatum C. Miill., from Montevideo, Uruguay, were located in the herbarium of the New York Botanical Garden, making it possible for the first time to give a complete description and illustration of this species. It is closely related to 0. araucarieti C. Mill. ex Broth., and known only from now urbanized areas of Uruguay and Argentina and not collected for 100 years. It is thus a species only known from extinct habitats. Among the unnamed specimens of Orthotrichum in the herbarium of the New York Botanical Garden were two collections from Montevideo, Uruguay. The collections were made in 1873 by Arechavaleta and Gibert, respectively. They represent a taxon with immersed or emergent capsules, superficial stomates, and double peristomes of the basic type within the subgenus Phaneroporum section Leiocarpa (cf. Lewinsky 1989). The plants were growing in small tufts on trees and are fastigiately branched. After examination it was clear the plants belong to O. truncato-dentatum C. MUill. (Mfiller 1882). This moss was previously only known from a fragment of the type collection present in Brotherus' herbarium in Helsinki, a fragment so small it was not possible to give a satisfactory description or illustration of the taxon. With the two new collections, which were made nine years before the species was actually described, it is now possible to do so for the first time. ORTHOTRICHUM TRUNCATO-DENTATUM C. Miill. (FIG. 1-2) ARGENTINA. Isla Recreo, 28 March 1880, Schnyder(lectotype, H). Plants in loose tufts, to 2 cm tall, olive-green above, blackish below; rhizoids only present at extreme base; stems fastigiately branched near apices; leaves spreading when moist, erect, appressed or slightly open when dry, lanceolate or ovate-lanceolate, shortacute or apiculate, 2.3-3.7 x 0.6-0.7 mm, somewhat carinate; costa ending a short distance below apex; margins entire, broadly revolute except for extreme apices and bases; basal leaf cells 30-90 x 9-14 ,m, rectangular to elongate-rhomboidal, with moderately thick, almost nonporose walls, smooth; cells in basal leaf corners slightly larger, sometimes brownish and decurrent; basal leaf marginal cells in several rows almost quadrate; upper leaf cells 6-15 x 6-12 lm, rounded-quadrate or rectangular, moderately thick-walled, with low mostly simple papillae; midcosta cells not differentiated. Gemmae not observed. Goniautoicous; perichaetial leaves not differentiated; capsules immersed or emergent, ovoid or ovoid-cylindric, 1.5-2.0 mm long, smooth or slightly furrowed just below mouth when dry; operculum conic, with short straight beak; exothecial cells not or only very little differentiated; stomates superficial, surrounded by radiating cells, few, in central and lower parts of capsules; peristome double, fragmentary preperistome sometimes present; exostome teeth 8, revolute when dry, pale orange, den ely and evenly papillose on outside, openly vertically papillose-striate on inside; endostome segments 8, lanceolate to triangular, almost or as tall as exostome, mostly with distinct median line on inside, pale yellow or hyaline, with thin smooth outer layer and thicker inner layer with open ornamentation of papillae and vermicular lines; spores globose, 18-25 gm, finely papillose, yellowishbrown; calyptra large, conic or conic-oblong, only slightly plicate, with scattered, thin, smooth hairs reaching to top. Additional specimens seen. URUGUAY. Montevideo, Arechavaleta 227, Gibert 1156 (NY). The Orthotrichum flora of Uruguay includes only three species: O. araucarieti Broth., O. truncatodentatum C. Mfill., and O. diaphanum Brid. var. podocarpi (C. Milll.) Lewinsky. All are epiphytes, and all are restricted to the southernmost part of the country (cf. Lewinsky 1985, 1987). Orthotrichum truncato-dentatum is closely related to O. araucarieti, also known from Brazil. The most distinct difference is found in the leaves and particularly the leaf apices. They are acute or apiculate in the former, acuminate in the latter. Additionally, the spores of O. truncato-dentatum are 0007-2745/92/218-220$0.45/0 This content downloaded from 157.55.39.102 on Mon, 03 Oct 2016 04:48:54 UTC All use subject to http://about.jstor.org/terms 1992] LEWINSKY: ORTHOTRICHUM TRUNCATO-DENTATUM 219
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