Jennings: Manual of Mosses — 5. Pottiaceae 11 



with central strand, radiculose below, thickly foliate, simple or more or less 

 branched; leaves pluri-seriate, rarely 3-seriate, lanceolate to broadly ovate or 

 obovate; costa heterogeneous, mostly percurrent, or excurrent, sometimes with 

 longitudinal lamellae or with green branched filaments on the ventral surface 

 above the middle; leaf-cells parenchymatous, the basal rectangular to elongate, 

 mostly pellucid, or hyaline, upper cells always chlorophyllose, on both sides 

 mostly warty papillose, loose, sometimes towards the apex 4-6-angled, or small 

 and rounded-quadrate; seta more or less elongate, mostly straight, rarely 

 almost lacking; capsule erect, symmetric, rarely slightly inclined, straight to 

 slightly arcuate, mostly oblong to cylindric, rarely oval to spherical; collum 

 short, rarely none; peristome various to none, mostly inserted on the mouth of 

 the urn, usually without projecting trabeculae; teeth 16, straight or spirally 

 twisted, often united at base into a tube, entire or 2-3-cleft into filiform- 

 subulate divisions, papillose; operculum mostly conic, rostrate; calyptra mostly 

 cucullate, smooth, rarely papillose or minutely bristly or short-hirsute. 



A very large family, mainly confined to the temperate zones, occurring 

 almost entirely on soil or on rocks. The systematic relationships and the 

 scope of the family are variously treated by different bryologists who have 

 taken different characters as the basis for the various classifications. This 

 family was called Tortulaceae in the first edition, but for purposes of uniformity 

 it is here called Pottiaceae, following Brotherus (Pflanzenfamilien, 2nd edit., 

 1924, and Grout, Moss Flora, 1938). 



Key to Genera 



A. Minute, bud-like plants with broadly ovate, concave or carinate leaves; cleistorarpous 



9. Acaulon 



A. Not as above B 



B. Leaves mostly narrow, often linear-lanceolate, never broadest above the middle 

 except some occasionally Imgulate in Gymnostomum calcareum; costa with sev- 

 eral guides, no accompanying cells, but 2 stereid bands, rarely longe.xcurrent C 



B. Leaves mostly broad, ovate-oblong ct spatulare or lingulate; costa with 2 median 

 guides, with accompanying cells, and 1 stereid band, mostly more or less lono- 



excurrent M 



C. Plants minute; areolation dense, strongly papillose: capsules cleistocarpous 



\. Astomum 



C. With deciduous operculum D 



D. Peristome none E 



D. Peristome present, rudimentary or well-deveIop>ed F 



E. Operculum deciduous with the columella detached 4. Hymenostylium 



E. Columella remaining in the urn after the falling away of the operculum 



3. Gymnostomum 



F. The exterior surface of the teeth more strongly developed and with projecting 



plates; leaves crispate when dry; seta long 2. Weisia 



F. Both surfaces of the teeth equally well-developed and no projecting plates G 



G. Perichaetial leaves long-convolute-sheathing 8. Barbida 



G. Perichaetial leaves not or but little convolute-sheathing H 



H. Leaves more or less lingulate, margins plane; cells smooth 7. Didymodon 



H. Leaves more or less lanceolate j 



J. Leaf-margins plane or involute; cells papillose K 



I. Leaf-margins more or less revolute; leaf-cells nearly smooth or papillo.e L 



K. Divisions of p>eristome erect or slightly dextrorsely twisted 5. Trkhostomum 



