240 American Midland Naturalist Monograph No. 6 



and branches, slenderly acuminate into a sub-channeled acumen, entire, the 

 base rounded to somewhat excavate and decurrent auricles, so that the inser- 

 tion is more or less of a semi-circle; median leaf-cells linear, rather incrassate> 

 about 10-15:1, reaching 0.3 mm or even longer, towards the base rapidly be- 

 coming shorter and quickly passing into large, hyaline, oblong, much-inflated 

 cells, thus forming a distinct patch reaching to the costa and, below, passing 

 abruptly into the narrowly linear epidermal cells of the stem; in cross-section 

 the stem may be seen to have the 3 or 4 outer layers small and very thick- 

 walled. 



In bogs and wet places, usually in cool or alpine regions; northern and 

 temperate Europe and Asia and, in North America, from Greenland to Alaska 

 south to the northern United States. 



Crawford Co.: In pools, Pymatuning Swamp, Linesville, August 19, 1904. Sterile. 

 O.E.J, (figured). Elk Co.: Midmont Swamp. Elev. 1940. C.M.B. July 1, 1948. Erie 

 Co.: Among cattails in swamp. Presque Isle, Nelle Ammons. July 22, 1933. McKp.an 

 Co.: Cathrine Swamp. C.M.B. Sept. 2. 1948. 



9. Calliergon (SuIIivant) Kindberg 



Mostly dioicous: more or less robust, stiffly and loosely cespitose, gi-eenish 

 to brownish or yellowish, rather lustrous; stem long, in v/ater and in deep 

 swamps not bearing rhizoids but assuming a more or less erect habit, in dry 

 places procumbent and bearing rhizoids, irregularly to regularly pinnatelv 

 branched; stem-leaves large, erect-spreading to imbricate, concave, rarely some- 

 what plicate, ovate to oblong or almost circular, the apex broadly rounded to 

 cucullate, the margin plane and entire or rarely so.mewhat revolute below; 

 costa mostly strong and almost complete, sometimes indistinctly forked at the 

 end; leaf-cells elongate, linear-hexagonal, shorter below, the alar forming! a 

 distinct group of large, quadrate, rectangular, and polygonal cells, at first thin 

 and hyaline but later colored and incrassate, the alar portion of the leaf exca- 

 vate; branch-leaves smaller, narrower, the apex often canaliculate; the inner 

 perichaetial leaves erect, more or less long-acuminate, mostly non-plicate, with 

 a simple costa: seta mostly very long, drying flat, red to castaneous; capsule 

 inclined to horizontal, thickly oblong to oblong-cylindric, more or less dorsally 

 gibbous, drying arcuate, smooth; annulus none to broad; peristome normally 

 hypnoid; lid convex, acute to obtuse-conic. 



A genus of about 15 species of aquatic, largely swamp- inhabiting; mosses, 

 confined to temperate and cold regions: 8 species occurring in North .America; 

 1 species within our range and others to be expected. 



Key to the Species 



A. Costa weak; alar cells incrassate 4. C. trifarium 



A.Costa strong; alar cells thin-walled and inflated B 



B. Costa extending to the middle or a little above 3. C. stramineum 



B. Costa sub-percurrent C 



C. Plants slender, simple or but sparingly branched; alar cells gradually enlarged and 



long-decurrent 1. C. cordifolium 



c. Robust and profusely branched; alar cells abruptly enlarged and inflated 



2. C. giganteum 



