OF WESTERX PENNSYLVANIA 73 



radiculose : leaves weakly or not at all auriculate, from the 

 lanceolate base long-subulate, canaliculate-tubulose, the 

 acumen often plainly toothed on the margin and dorsal sur- 

 face of the costa by reason of the mammillate cells ; costa broad 

 and flat, long, excurrent, and almost filling the acumen ; alar 

 cells reaching the costa, inflated, hyaline, sometimes reddish, 

 delicate, areolation above the alar cells widened to- 

 wards the costa and rectangular to long-hexagonal, at the 

 margin usually united into a more or less broad border; 

 perichsetial leaves sheathing, abruptly long-subulate : seta 

 arcuate, finally erect-flexuous ; capsule symmetric, oblong- 

 cylindric, smooth ; annulus not differentiated ; peristome in- 

 serted below the edge of the capsule-mouth ; teeth separate, 

 two-parted deeply, or to the base, the divisions filiform-subu- 

 late, below vertically and above obliquely striate-papillose ; 

 calyptra cucullate. 



A cosmopolitan genus of 21 species; 4 species in North 

 America; 3 species occurring in our region. 



Key to the Species. 



a. Peristome-teeth cleft to base: leaves with somewhat widened 

 auricles. i. D. longirostre. 



a. Peristome-teeth not cleft to base: leaves non-auriculate. 



b. 

 b. Leaves easily caducous: seta 1.5-2 cm., urn 1.5-2 mm. long. 



2. D. virginicttm. 

 b. Leaves rather peristent: seta 5-8 mm., urn 1 mm. long. 



3. D. mills paughii. 



1. Dicranodontium longirostre [Starke] Bryologia Europsea. 

 {Didymodon longirostris Starke). 

 (Plate IX.) 

 Densely and softly cespitose, lustrous, pale green, when 

 dried as in herbarium-specimens often a lustrous yellowish- 

 brown: stems erect or ascending, up to 3 or 4 cm. high, fork- 

 ing frequently, flexuous, radiculose below; leaves rather 

 numerous, often quickly deciduous, from a more or less sheath- 

 ing oblong concave base with more or less widened auricles 

 gradually narrowed to a long, flexuous-spreading or falcate- 

 secund, linear-subulate or setaceous, tubulose point, the margin 

 entire to faintly denticulate towards the apex; costa strong, 

 one-fifth to one-third the width of the leaf at base, excurrent 

 in the rough subulation, in cross-section showing a median 

 row of large hyaline cells bordered on either side by minute 

 incrassate cells ; alar leaf-cells large, inflated, hyaline to brown- 

 ish, rectangular, above becoming incrassate and narrower, in 

 the oblong base the upper marginal cells elongate-linear and 

 more or less prosenchymatous, the median and upper rounded- 

 quadrate, varying to short-rectangular or oblong: seta cygne- 

 ous, dextrorse ; capsule oblong-cylindric, small ; peristome- 



