OF WESTERN PENNSYLVANIA 171 



F'amily XVII. MEESBACEAE. 



Synoicous, autoicou3, dioicous, or polyoicous : robust to 

 slender, cespitose : stem with a central strand, elongate, leaves 

 3-8-seriate, moderately close, mostly from an erect base erect- 

 spreading to recurved-squarrose, lance-ovate to lance-acumi- 

 nate, non-bordered, sometimes toothed at the apex ; costa strong, 

 without guides, mostly incomplete; cells mostly parenchyma- 

 tous and smooth, upper firni-walled, rectangular to rounded 

 4-6-sided, the basal often thin-walled, elongate-rectangular 

 and hyaline : seta mostly long and slender, erect, tortuous ; cap- 

 sule erect, from a long collum elongate arcuate-pyriform, the 

 mouth small and oblique, never constricted below the mouth ; 

 annulus small-celled, 1-2-seriate, loosening itself here and 

 there, rarely persisting; teeth mostly much shorter than the 

 segments, truncate, more or less completely confluent, with 

 straight divisural and thin rectangular dorsal plates, the inner 

 layer with low lamellae; inner peristome with a carinate basal 

 membrane united to the teeth; segments narrowly linear, 

 alternciting with the teeth, cilia rudimentary or none ; spores 

 .032-056 mm., mostly finely granulate ; operculum small, conic, 

 obtuse; calyptra small, cucullate, smooth, fugacious. 



A small family (3 genera) of mostly bog mosses of the 

 cooler parts of the northern hemisphere. One genus repre- 

 sented in our range. 



1. MEESEA Hedwig. 



Characters mainly as for the family ; the tufts green to yel- 

 lowish-green, inside brown to blackish : leaves more or less de- 

 current, acute or obtuse, mostly entire; upper cells mostly 

 rectangular, thick-walled, the lower elongate and hyaline : seta 

 usually very long, inner peristome with a very low basal mem- 

 brane ; segments 2 to 4 times the length of the teeth, often more 

 or less united at the tip ; cilia short or rudimentary, often being 

 represented by a chain-like series of thickenings on the per- 

 sisting wall of the inner peristome. 



Nine species in bogs and wet places ; fQur species in North 

 America; two species may be looked for in bogs and swamps 

 in the northern part of our region. 



Key to the Species. 



a. Leaves three-ranked, serrate. 1. M. triquetra. 



a. Leaves S-8-ranked, entire. (M. longiseta Hedwig). 



1. Meesea triquetra [Linnaeus] Aongstroem. 

 (M. tristicha. (Funck) Bryologia Europsea.) 

 Loosely cespitose, dark green: stems elongate, radiculose 

 below, sparingly branching; leaves three-ranked, distant. 



