OF WESTERN PENNSYLVANIA 169 



1. AULACOMNIUM Schwaegrichen. 



^\'lth characters as for the family, the stem sometimes 

 bearing fliagelliform pseiidopodia, which are leafless or nearly 

 so atid bear a cluster of gemmte at the tips ; leaves crowded, 

 erect-ascending, the margins more or less revolnte ; costa 

 ending below apex ; cells each with a central papilla ; capsule 

 somewhat arcuate ; annulus 2-4-seriate, revoluble ; teeth lance- 

 linear and subulate-acuminate, yellow to rusty, the divisural zig- 

 zag, finely papillose, with numerous articulations ; inner peris- 

 tome delicate, hyaline ; segments lance-subulate, gaping ; cilia 

 well developed, delicate, mostly only weakly articulate ; nine 

 species widely distributed ; five in North America, two in our 

 range. 



Key to the Species. 



a. Autoicous; leaves strongly serrate from the middle upwards. 



1. A. hclerostklnuii. 

 a. Dioicous; leaves merely serrulate near the apex. 



2. A. paliistrc. 



1. Aulacomnium heterostichum (Hedwig) Bryologia Europsea. 



(Arrhenopteruni heferosticluiin Hedwig). 



(Plate XXIV) 



Rather loosely cespitose, pale to yellowish-green : stems 

 branching by terminal, annual innovations, the annual growth 

 in our specimens being usually about 8-10 mm., stems brown- 

 radiculose below ; leaves obovate below to oblong or oval 

 above, often somewhat unsymmetrically inclined, the leaf 

 plane above, repand denticulate in the upper half, mostly apicu- 

 late ; costa strong, yellowish-brown, ending just below apex; 

 leaf-cells incrassate, median and apical rounded-quadrate, 

 about .008-.015 mm. in diameter, basal similar, quadrate to 

 rectangular and 3:1 : seta about 6-9 mm. long, erect, flexuous, 

 reddish-brown, smooth, little or not at all twisted, capsule 

 about 2.5 mm. long, oblong-cylindric, arcuate, inclined, red- 

 dish-brown, striate, when dry 8-plicate, tapering below into a 

 short collum ; annulate, doubly peristomate ; teeth inserted on 

 the capsule-rim, lanceolate, about 25-30-articulate, distinct 

 to the base, yellowish-pellucid, rather indistinctly finely hori- 

 zontally striate-papillate below, segments of same length or 

 a little shorter, hyaline, more or less completely carinate-cleft 

 in median portion, united in the lower third with the cilia 

 into a basal membrane: cilia 3 (2), somewhat shorter, some- 

 what articulate ; spores pellucid-yellowish, not distinctly papil- 

 lose, about .012-.014 mm. ; mature in May to June ; operculum 

 convex, obtusely short-rosttate ; calyptra long-rostrate, cucul- 

 late. 



