OF WESTERN PENNSYLVANIA 257 



Key to the Species. 



a. Delicate, small, not over 5 cm.; 1-2-pinnate. 



b. 

 a. Larger, up to 10 cm.; 1-3-pinnate. c. 



b. Branchlets papillate: leaf-cells about .006 mm.: seta 1-2 cm. 

 long. (T. pygmaeum (Sull.) 



Bryol. Enr.). 

 b. Branchlets smooth; cells about .009 mm.: seta 2-4 cm. long. 



1. T. uiinutuluni. 

 c. Stems simply pinnate; plants ascending in tufts. 



(T. abictinum [L,.] 



Bryol. Eur.). 

 c. Stems 2-3-pinnate, forming flat mats. d. 



(1. Leaf-margin re volute; costa not filling entire apex of leaf. 



e. 

 d. Leaf-margin plane; costa of stem-leaves filling the entire apex; 



perichjetial leaves not ciliate. 3. T. recognititm. 



e. Stem-leaves lance-acuminate: perichsetial leaves ciliate. 



2. T. delicatulum. 



e. Stem-leaves long-lance-subulate; perichaetial leaves not ciliate. 



(T. philiberti Limpricht). 



1. Thuidium minutulum [Hedwig] Bryologia Europaea. 



(Hypnum minutulum Hedwig). 



(Plate XXXV) 



Small, slender, simply pinnate ; steins irregularly divided, 

 not over 3 or 4 cm. long, both stems and branches smooth, 

 bearing rather few linear-oblong simple paraphyllia only about 

 2 to 5 cells high, notched at apex; stem-leaves distant, deltoid, 

 acuminate or apiculate. somewhat re volute on the borders, 

 rather opaque, about 0.6-0.8 mm. long; costa strong, ending 

 near the apex; median leaf-cells irregularly polygonal to 

 quadrate-hexagonal, the marginal somewhat larger and some- 

 times transversely elongate, all leaf-cells incrassate, pluri- 

 papillose, the apical cell with 2 to 5 marginal papilla?; branch- 

 leaves ovate-acuminate, about 0.2-0.3 mm. long, concave and 

 with a shorter costa ; perichaetial leaves erect, slenderly lance- 

 acuminate, the acumen more or less reflexed : seta about 2-2.5 

 cm. long, slender, dark yellow or brown and sinistrorse when 

 old ; capsule yellowish, oval-oblong, cernuous to horizontal, 

 the urn about 2 mm. long, when dry somewhat constricted 

 below the rim ; lid obliquely subulate-rostrate and about 1 

 mm. long ; peristome castaneous, the teeth slender, densely 

 trabeculate, the dorsal lamella? cross-striate and projecting to 

 form a narrow margin, the divisural distinct ; segments as long 

 as the teeth, split carinately, arising from a basal membrane 

 about one-third as high, cilia usually 2, articulate, nearly as 

 long; spores about .010-.012 mm., pale brown, medium-walled, 

 slightly roughened, mature in fall. 



