OF WESTERN" PENNSYLVANIA 153 



-trongly appendicnlate, slightly shorter than .segments, basal 

 membrane one-half height of teeth : spores yellowish-pellucid, 

 smoothish or minutely -roughened, about .014-.016 mm.; 

 exoihecial cells incrassate. rectangularly quadrate or hexa- 

 gonal, the upper three or four rows much smaller and rounded 

 to transversely elongate and darkly reddish-pellucid: gonio- 

 autoicous. antheridia in apex of the lateral innovations : ma- 

 ture in May or June. 



In crevices of walls and sandstone rocks. Europe, Asia, 

 northern Africa, Xorth America from Greenland to British Co- 

 lumbia and south to the northern United States. Rare in our 

 region. 



Alle^'henv : On debris in rock-crevices along sand- 



o * ... 



stone cliff facing the Allegheny River at 

 Power's Run. April 28, 1907. O. E. J. 

 ( Figured). 



7. Bryum caespiticium | Linnseus] Hedwig. 



(Plate XX) 



Densely cespitose, yellowish-green : stems erect, rarely 

 more than 1 cm. high with us. branching by lateral innovations, 

 brownish-tomentose below, reddish above : leaves remote and 

 small below, the upper densely tufted, ovate to lanceolate or 

 narrower within, concave, narrowly acuminate, borders re- 

 curved, the apex slightly denticulate or sometimes entire, the 

 base often reddish, the comal reaching 3-3.5x1 mm., when dry 

 but little shrunken or tw isted ; costa strong, reddish, long-ex- 

 current : leaf-cells narrow-rhomboid, becoming larger and 

 rectangular at base, the marginal in one to three rows of linear- 

 prosenchymatous incrassate cells but not forming a very pro- 

 nounced border: set erect, slender, rlexuous. lustrous-castane- 

 ous. about 2 1- cm. long, rarely more ; capsule oblong-pyriform. 

 3-3.5 mm. long, yellowish-brown to darker with age, the neck 

 comprising almost one-half the capsule, horizontal to pendu- 

 lous, sometimes unsymmetrically up-curved, constricted below 

 the mouth \vhen dry and empty : the mouth darker colored : 

 peristome-teeth yellowish-pellucid below, paler and minutely 

 papillose above, linear-lanceolate ; segments of inner peristome 

 almost as long, somewhat yellowish, carinately split and gap- 

 ing, cilia as long as segments or almost so, strongly appendicu- 

 late, basal membrane about two-fifths the height of teeth ; 

 spores about .012-.017 mm., smoothish, yellowish-pellucid; 

 exothecial cells incrassate, rectangular below to irregularly 

 quadrate-hexagonal above, the upper three or four rows much 

 smaller and rounded-quadrate to laterally elongate and 

 colored: operculum usually orange-brownish, mamillate to 

 conic-apiculate : dioicous : mature in May to June or July. 



