96 American Midland Naturalist Monograph No. 6 



lanceolate from an oblong or ovate base, acuminate, entire, margins plane or 

 revolute; costa complete or extending to the base of the piliferous apex; upper 

 cells small, rarely papillose, rounded-quadrate, often opaque, looser towards 

 the middle, the basal linear to rectangular, mostly smooth-walled, and some- 

 times forming a colored border; perichaetial leaves mostly larger, more or less 

 sheathing, areolation looser: seta sometimes shorter than the capsule, rarely 

 much longer than the perichaetial leaves, arcuate or straight, mostly yellow, 

 twisted when dry, capsule mostly symmetric, smooth to ribbed, globose to 

 cylindric; annulus persistent or curling off, sometimes none; peristome rarely 

 absent, when present inserted below the mouth; teeth reddish-brown, broad to 

 subulate, entire to cribrose, sometimes cleft to the middle, the trabeculae pro- 

 jecting outwards; operculum often rostrate, never longer than the urn; calyptra 

 lobed-mitrate to cucullate, long-rostrate, smooth; spores small, .010-. 012 mm 

 diameter. 



A large genus of world-wide distribution, but mainly confined to the moun- 

 tains of the tropics, occurring on rocks and stones. About 230 species, of 

 which more than 90 occur in North America and at least 4 in our region. 



Key to the Species 



A. Seta not longer than the capsule; operculum mostly falling with the columella still 



attached; hyaline leaf-points decidedly spinulose B 



A. Seta longer than the capsule F 



B. Apices of upper leaves with short hair-points C 



B. Apices of upper leaves long-piliferous E 



C. Lower and median leaf-cells with sinuose walls 4. G. laevigata 



C. Lower leaf-cells not with conspicuously sinuose walls D 



D. Slender small plants in dense cushions; central strand in stem; teeth decidedly 



cribrose or cleft 2. G. confertj 



D. More robust, loosely cespitose; with indistinct central strand; teeth slightly cribrose 



or entire - 1. G. apocarpa 



E. Leaf-cells without sinuose walls; capsule oblong; calyptra often cucullate, 



( G. ambigua [Sullivant] Sullivant ) 



E. Leaf-cells with somewhat sinuose walls; capsule oblong-ovate 3. G. pilifera 



F. Capsule distinctly ribbed; seta curved; leaf-margins of a single layer of cells 



(G. Olneyi Sullivant) 



F. Capsule smooth, seta straight; upper leaf-margins of more than one layer of cells ....G 

 G. Leaves lanceolate, tapering; basal leaf-cells thin-walled and elongate-rectangular, 



about 1:4 to 1:8, alpine (G. obtusa Schwaegrichen; G. Doniana Smith) 



G. Leaves ovate to oblong-lanceolate, the long apex rough, piliferous; basal leaf-cells 



more or less quadrate 4. G. laevigata 



1. Grimmia apocarpa [Linnaeus] Hedwig 



Plate XVIII 



Loosely cespitose, more or less erect, branching rather freely, about 2 cm 

 high, dull olive-green, drying stiff and ncn-crisped: leaves ovate-lanceolate, 

 erectinp-spreading, strongly costa te and usually more or less carinate, margin 

 narrowly recurved, apex narrowly obtuse, leaves about 2 mm long; perichaetial 

 leaves similar but somewhat longer and thinner; costa ending in or just below 

 the apex, terete dorsally; basal cells rectangular, about .008-010 x .015.030 mm, 

 upper basal cells quadrate, and in our specimens usually sinuose-walled, the 



