OF WESTERN PENNSYLVANIA 79 



able to find this species along Slippery Rock 

 Creek, where Lesquereux found it. 



2. fISSIDENS Hedwig. 



Autoicous or dioicoiis : stem short to long, erect to pro- 

 cumbent, more or less branched or simple ; leaves prominent- 

 ly winged, linear-obovate to lanceolate-obovate ; costa usually 

 present ; cells rounded-hexagonal, sometimes loosely rhom- 

 boidal, rarely prosenchymatous, smooth or papillose : seta 

 erect or ascending", long to short, mostly terminal, sometimes 

 lateral ; capsule mostly exserted, erect or inclined, symmetric 

 oi unsymmetric ; peristome mostly inserted below the mouth 

 of the urn, teeth cleft, exteriorly articulate, often striate- 

 papillose ; spores mostly small ; operculum conic to rostrate ; 

 calyptra entire to once or rarely several times cleft, mostly 

 smooth. 



A widely distributed genus of about 550 species, mainly 

 tropical, on soil, rocks, trees, humus, or in water. In our 

 region at least 8 species. 



Key to the Species. 



a. Costa none: minute plants 2-4 mm. high. i. F. hyalinus. 

 a. Costa well developed. b. 



b. Leaves bordered, at least on the vaginant lamina, by a band 

 of linear cells. c. 



b. Leaves not bordered, or at least the border not composed of 

 linear cells. g. 



c. Costa percurrent, confluent with border at apex and forming a 



mucro: capsule erect. 2. F. bryoides. 



c. Costa not usually percurrent; border not usually reaching apex: 



capsule curved or erect. d. 



d. Leaves non-bordered, entire, obtuse. 3. F. ohtusifolius. 



d. Leaves bordered, at least on sheath, acute or apiculate. 



e. 

 e. Leaves bordered to near the apex. f. 



e. Leaves usually bordered only on the sheath. 



5. P. exigmts. 



f. Leaves broadly oblong-lanceolate: capsules usually more or 

 less curved: plants usually more than 2 mm, 



4. F. incnrvus. 

 f. Leaves narrowly oblong-lanceolate: capsules usually erect: 

 plants often less than 2 mm, high. 4a. F. inc. vtimitr.liis. 



g. Leaves without a marginal band of several rows of somewhat 

 paler cells, the outer row sometimes paler. 



L 

 g. Leaves with a marginal band of several rows of paler incrassate 

 cells. h. 



h. Leaf-cells rather obscure, about .006-.010X.006-.014 mm. 



6. F. cristatus. 

 h. Leaf-cells distinct, about .012-.016X.01S-.O25 mm. 



7. P. adiantoides. 

 i. Costa excurrent into the apiculus. 8. P. taxifolius. 



I. Costa not. quite reaching ape.x. j. 



j. Leaves apiculate: seta terminal: leaf-cells .010-.016X.014-.020 

 mm. 9. P- osmundioides. 



