OF WESTERN PENNSYLVANIA 75 



of the urn dark colored: lid about as long as the urn (1 mm.), 

 straight, subulate-rostrate; spores maturing in summer: 

 dioicous. 



At the southern border of our region on sandstone rock in 

 deep woods along Tibbs Run, Monongalia County, West Vir- 

 ginia. C. F. Millspaugh. 



Family III. LEUCOBRYACEAE. 



Dioicous, rarely autoicous ; densely cespitose and more or 

 less spongy like Sphagnum, whitish to glaucous-green : stem with- 

 out central strand, scarcely radiculose ; leaves pluriseriate, 

 close, quite uniform in size ; costa very broad, constituting 

 most of the leaf, sometimes narrow with a stereid-bundle, 

 composed of two kinds of cells, the outer large and parenchym- 

 atous with perforated inner walls, the inner smaller and 

 chlorophyllose, the lamina hyaline, usually very narrow and 

 mainly basal : seta single, erect ; capsule erect and symmetric 

 or inclined, unsymmetric and strumose ; annulus none; peri- 

 stome usually inserted below the edge of the urn, the teeth 

 mostly 16, sometimes only 8, lanceolate, articulate, entire or 

 cleft to the middle; operculum conk, rostrate; calyptra 

 cucullate or sometimes mitrate. 



With the exception of the genus Leucobryum the species of 

 this family are mostly tropical or sub-tropical in their distribu- 

 tion and occur mainly on trees. In our region there occurs 

 only the following genus : 



i. LEUCOBRYUM Hampe. 



Dioicous : thickly to loosely cespitose ; whitish or glaucous 

 green, mostly lustrous : leaves erect, when dry appressed and 

 brittle, sometimes spiral, or falcate, or squarrose-spreading, 

 from an ovate base lanceolate- to subulate-acuminate, canalicu- 

 late or sometimes almost tubulose above ; costa flat, the large 

 parenchymatous outer cells 2-6-layered ; lamina mostly nar- 

 row, often vanishing below the apex, without a border ; 

 perichaetial leaves half-sheathing and long-acuminate : seta 

 terminal, or lateral by the growth of innovations, long; capsule 

 more or less arcuate, unsymmetric. often strumose, with 8 rib- 

 like projecting ridges; peristome on the edge of the urn, the 

 teeth united at base into a tube, cleft to the middle into two 

 lance-subulate prongs, thickly trabeculate, vertically striate 

 and papillose ; operculum subulate from a conical base ; 

 calyptra inflated, cucullate, covering the urn. 



About 106 species, mostly in the tropics, on trees, rocks, 

 or on shaded earth ; 16 occurring in North America ; 2 species 



in our range. 



