The Identity of Grimmia involucrata Cardot (Grimmiaceae, Musci)

Abstract

Grimmia involucrata is a Mexican en- demic that has been confused with G. affinis, G. americana, and G. tergestina. It is recognized here as a valid, morphologically distinct species char- acterized by clavate stems, a gonioautoicous con- dition, differentiated perichaetial leaves, immersed sporophytes, and the smooth basal third of the outer plate of the peristome teeth. It is illustrated herein. Grimmia involucrata was described by Cardot (1909) on the basis of a specimen collected in the state of Hidalgo, Mexico. Reference to this species was made by Thgriot (1931), who listed specimens collected by Amable in Mexico City; Sayre (1952) and Whitehouse and McAllister (1954) treated it as conspecific with G. americana Bartram, a species described from Texas (Bartram, 1929). Crum and Anderson (1981: 424) disagreed and concluded that G. involucrata was not even a member of the when dry, erect-spreading when moist, oblong- ovate, 0.9-1.3 mm in length; apex obtuse; distal leaf margins bistratose, plane, entire. Distal leaf cells quadrate to short rectangular, in 2(-3) layers of thick-walled, slightly sinuose cells, 5-12 im diam.; marginal leaf cells at base quadrate to short rectangular or transversely elongated, with thicker cross walls, 7-17 im diam.; other basal cells uni- stratose, quadrate to rectangular, thick-walled, slightly sinuose upward; basal juxtacostal cells not forming a distinct area, mostly quadrate and thin- walled. Costa excurrent, in section with one dorsal substereid layer and 2-6 guide cells around or ven- tral to an internal hydroid group. Hair-point 0.6- 1.3 mm long, denticulate, slightly decurrent at base. Gonioautoicous. Perigonial bracts convolute, 0.6 mm long. Perichaetial leaves strongly differ- entiated, the outer with a hyaline marginal area, the inner mostly thin-walled and hyaline; oblong-ovate to convolute, 1.4-1.9 mm long; hair-point 0.9-1.6 mm long. Seta straight, 0.5 mm long, not twisted. Capsule symmetrical, ellipsoid, immersed, 1.2-1.4 mm long; peristome teeth somewhat cribrose, del- toid, 287-300 x 62-75 jm, straw-colored to or- ange, outer plate nearly smooth in the lower third, trabeculate, distally papillose; inner plate finely pa- pillose throughout; annulus revoluble; exothecial cells prismatic, mostly longer than wide, thin- walled, 25-60 im diam.; stomata several, basal; operculum conic, short-rostrate, 0.7 mm long; ca- lyptra mitrate, smooth, 0.9-1 mm long. Spores 10- 15 Ism diam., spore wall perforated.