OF WESTERN PENNSYLVANIA 221 



3. THAMNIUM Bryologia Europsea. 



(Porotrichum Bridel). 



Dioicous or, rarely, autoicous : mostly robust to very 

 robust, with a long, creeping primary stem: the primary stem 

 has scale-like leaves, and is more or less densely brown-radicu- 

 lose ; the secondary stem erect to ascending, writhout branches 

 below, stoloniferous, somewhat dendroid in habit; branches 

 spreading, flattened, obtuse ; leaves erect-spreading to spread- 

 ing, plane to concave, smooth to plicate, not rugose, non-de- 

 current, unsymmetric, mostly oblong to ovate or ovate-lingu- 

 late, the apex obtuse to acute, serrate ; costa strong, mostly 

 incomplete ; median leaf-cells parenchymatous, the basal some- 

 times linear ; inner perichjetial leaves lanceolate-acuminate and 

 spreading from a half-sheathing base : seta various, mostly 10- 

 15 mm. long, in certain species not more than 4 mm., in others 

 up to 4 cm. long, red, smooth ; capsule inclined to horizontal, 

 arcuate, .gibbous, rarely erect, symmetric, and oval ; annulus 

 revoluble : peristome-teeth lanceolate to linear, subulate-acumi- 

 nate, yellowish, bordered, with a zigzag divisural ; inner peris- 

 tome pale yellow, basal membrane prominent, segments broad, 

 carinately split and gaping ; cilia often appendiculate ; spores 

 small ; lid conic, rostrate ; calyptra cucuUate, glabrous. 



About 41 species in temperate and warm regions ; 7 species 

 in North America; one species in our region. 



1. Thamnium allegheniense (C. Mueller) Bryologia Europsea. 

 (Hypntiin allegheniense C. Mueller). 

 (Plate XXXII) 

 Large, dendroidal in habit, bright to pale green, usually 

 rising to a height of 4-7 cm. ; leaves of the branches and branch- 

 lets up to 3 or 3.5 mm. long, rather lustrous and sub-plicate 

 when dry, erect-spreading, oblong-elliptic, short-pointed, con- 

 cave, the base somewhat narrowed but scarcely concave, the 

 apex broadly acute, the plane margin strongly serrate above; 

 costa strong, extending to near the apex; leaf-cells incrassate, 

 the median shortly rounded- or rhomboid-hexagonal, about 

 2:1, the basal becoming elongate-oblong, varying to elongate- 

 rectangular, the lower marginal and angular, scarcely wider 

 but sub-rectangular to quadrate; perichsetial leaves erect, 

 sheathing, narrowly acuminate, ecostate: seta lustrous, of a 

 rich castaneous color, usually about 1 cm. long, smooth, arcuate; 

 capsule oblong-cylindric, castaneous and rarely somewhat 

 wrinkled when dry, about 2-2.5:1, about 2 to 2.5 mm. long, 

 nearly symmetric but by the curving of the pedicel inclined or 

 horizontal, sometimes curved ; lid conic, long- and stout-ros- 

 trate, the whole lid being about one-half to one-third as long 

 as the urn ; peristome normally hypnoid, large ; teeth lance-sub- 



