64 A MANUAL OF MOSSES 



8. RHABDOWEISIA Bryologia Europaea. 



Autoicous: low, densely cespitose: stem without central 

 strand, in cross-section obtusely pentagonal, densely foliate, 

 radiculose, branched; leaves when dry crisped, decurrent, 

 linear to linear-lanceolate, acute, plane-margined ; costa strong, 

 disappearing below the apex; upper leaf-cells chlorophyllose, 

 quadrate to rounded, smooth ; basal cells rectangular and hya- 

 line: seta straw-yellow, erect; capsule erect, minute, sym- 

 metric, ovate to oblong, obtusely octagonal with darker striae, 

 8-costate when dry; annulus none; peristome rarely absent, 

 inserted on the rim ; teeth arising from low, broad, more or 

 less united bases, abruptly filiform or subulate, reddish-yellow, 

 trabeculae prominent ventrally but articulations scarcely pro- 

 jecting dorsally, surface of teeth non-papillose but often ob- 

 liquely minutely striate; operculum long-subulate, obliquely 

 rostrate, as long or longer than the urn ; calyptra cucullate, 

 rostrate, reaching to the middle of the capsule. 



About 8 species of the Northern Hemisphere, inhabiting 

 crevices of silicious rocks ; 5 species in North America ; 2 

 species in our region. 



Key to the Species. 



a. Leaves entire or nearly so. I. R. fugax. 



a. Leaves rather coarsely denticulate towards the apex. 



2. R. denticulata. 



I. Rhabdoweisia fugax (Hedwig) Bryologia Europaea. 

 (Weisia fugax Hedwig). 

 (Plate VH) 

 Densely cespitose, usually dark green: stems short, in 

 ours about 5 mm. high, radiculose at base ; leaves lance-linear, 

 recurved-spreading, numerous, about 2-2.5 mm. long, usually 

 somewhat concave, acute to shortly acuminate, margins plane, 

 faintly denticulate towards apex, leaves crisped when dry ; 

 costa strong but not quite reaching apex; upper leaf-cells 

 rounded-hexagonal, about .01Q-.014 mm., incrassate, chloro- 

 phyllose, papillose, rather yellow, arranged in rows, in the 

 upper part of the leaf about 6 or 8 rows on either side of the 

 costa, the apical cells larger and more hyaline, the basal cells 

 pellucid and elongate-rectangular, about 2-8:1: seta erect. 2- 

 3 mm. high, yellowish ; capsule erect, symmetric, oval ; the 

 urn wide-mouthed, about 0.5-0.7 mm. high, brownish, when 

 dry and empty 16-striate; operculum about as long as urn, 

 obliquely rostrate from a broad base; peristome-teeth abrupt- 

 ly subulate from a broad base, small, not very persistent, 

 articulate, papillose; spores about .018-.020 mm., minutely 

 roughened, yellowish-pellucid, maturing in mid-summer; 

 calyptra cucullate, covering about two-thirds of the urn ; exo- 



