100 American Midland Naturalist Monograph No. 6 



North America, from Greenland to British Columbiaj^ south to Oregon and 

 northeastern United States. Perhaps to be expected in the eastern or north- 

 eastern part of our region. 



3. Rhacomitrium heterostichum var. ramulosum (Lindberg) Jones 



(R. ericoides (Schwaegrichen) Jennings; Trichostemum ericoides Schwaegrichen ) 



Cespitose in low, green to yellow-green tufts: stems slender, markedly 

 nodose with obtuse lateral innovations; leaves crowded, spreading to falcate- 

 secund, lanceolate from an ovate base, acuminate, the apex hyaline, flat, den- 

 ticulate, not very narrow, margin revolute, not thickened; costa strong, ending 

 in the apex; leaf-cells all linear, the upper 3-6:1, incrassate, sinuose, the mar- 

 ginal shorter and in the alar portion often a few larger, rectangular, pellucid, 

 and not sinuose-walled: seta yellowish, short; capsule small, elliptic-cylindric 

 to oblong, pale yellow-brown, thin-walled; annulus large, revoluble; peristome- 

 teeth short, divided almost to the base; calyptra somewhat papillose at the 

 apex; lid short-rostrate; spores mature in spring. 



On exposed rocks and stones in hilly or mountainous regions, Europe, and, 

 in North America, from Greenland to British Columbia south to Oregon, 

 eastern Pennsylvania and Georgia. Perhaps will be found in the eastern part 

 of our region. 



3b. Rhacomitrium heterostichum var. gracilescens Bry. eur. 



Plate LII 



When dry forming crisped, blackish-green, dense tufts about 1 cm deep, 

 the prostrate stems 1-3 cm long and sending up short, irregularly spaced 

 upcurvied branchlets which, when dry have closely appressed leaves and are 

 less than 1 mm thick; when wet the leaves spreading-ascending or somewhat 

 recurved- spreading; leaves about 2 mm long, concave, from a broader base 

 slenderly lanceolate to a narrow, obtuse, entire apex, the base sub-clasping, the 

 margins entire, thickened and imperfectly bi-stratose, narrowly revolute; costa 

 50-60 jW, thick, prominent dorsally, percurrent into the somewhat cucullate leaf- 

 apex, bi-stratose with usually 2-3 smaller interior cells; basal cells enlarged, 

 somewhat colored in a narrow basal band, with a few somewhat larger rounded 

 alar cells, above these the cells rapidly becoming strongly incrassate and sinu- 

 ose, the median lower about 3-3.5 by 8-10 /<,, these at the apex roughly rounded 

 and about 2.5/j, in diameter. Some of the upper cells appear faintly papillose. 



The specimen here described and figured was collected by Charles M. 

 Boardman on rocks at Beck Spring, Laurel Ridge, Somerset Co., s.w. Pa., 

 July 26, 1947, and seems best placed under the polymorphic R. heterostichum, 

 nearest to var. gracilescens, although were the cells papillose it might as well be 

 referred to R. protensum Braun. The variety gracilescens is a very rare alpine 

 moss found in the U. S. on Bald Mountain, near Camden, Maine. 



Family 8. Orthotrichaceae 

 Dioicous or autoicous, rarely heteroicous or polyoicous: cespitose, light 

 green to yellowish- or blackish-green outside the tufts, inside brown to black: 



