28 American Midland Naturalist Monograph No. 6 



their thick walls very narrowly exposed on both surfaces, exceeded dorsally by 

 the convex outer walls of the hyaline cells. 



This is a far northern species with a reported range south to Connecticut, 

 New York, Minnesota, and British Columbia, hence this collection is a further 

 extension of range southwards. 



Columbus Bog, northern Warren County, Pa., Charles M. Boardman, Sept. 1, 1948 

 (figured). 



This species is easily distinguished by the fascicles of 6-12 branchlets and 

 also by the dense capitulum of short apical branchlets. 



Subsection II. Rigid a 



With short, densely placed branches, and forming dense tufts. Cortical 



cells of the branches each with a pore at the upper end. Chlorophyllose cells 



of branch-leaves small, elliptic, completely enclosed but nearer the dorsal 



(outer) surface of the leaf. Branch-leaves ovate, ending in an involute, mostly 



widely spreading or ascending apex. 



7. Sphagnum compactum DeCandol'le 



(S. rigidum Schimper) 

 Plate III 



Densely cespitose, gray-green or glaucous-green, brownish above, below 

 whitish or grayish-brown compactly and closely short-branched; stems stout, 

 low, in ours 4-8 cm high, with a cuticular sheath of usually 3 layers of cells, 

 the outermost cells largest, non-fibrillose, the wood-cylinder decidedly castan- 

 eous or sometimes yellowish; stem-leaves very small, 0.6-0.8 mm long, broadly 

 to equilaterally triangular-lingulate, the apex concave and broadly rounded or 

 truncate, erose-dentate, the margins rather widely hyaline-bordered; hyaline 

 cells of stem-leaves broadly rhomboidal, non-porose, non-fibrillose; branches 

 short, usually not over 1 cm long, 3 or 4 to a fascicle, horizontally spreading 

 or somewhat upcurved, the others slender and appressed-pendent; branch-leaves 

 when dry with the upper half of the leaf more or less squarrose-spreading, 

 large, 2-3 mm long, ovate, concave, the margins narrowly bordered, the uppsr 

 margins involute and often slightly erose-ciliate or erose-dentate the apvex 

 erose-dentate and cucullate; hyaline cells of branch-leaves rather broadly 

 rhomboidal, fibrillose, dorsally with several large, round pores irregularly 

 scattered and also in the cell-angles, the pores about two-fifths as wide as 

 the cell, sometimes a few oval and lateral, ventrally the pores sm.all, oval, 

 an^. located in the cell-angles; in cross-section the chlorophyllose cells are 

 elliptic, enclosed both dorsally and ventrally by the moderately convex hyaline 

 cells; cuticuar cells of the branches arge, short-rectangular, with one large 

 apical pore; fruit not seen. 



Our plants seem to be the variety squarrosum Russow (Roth. Die Euro- 

 paeischen Torfmoose, p. 14. 1906) (5. rigtdum var. squarrosum Russow. 

 Braithwaite. The Sphagnaceae or Peat Mosses of Europe and North Amer- 

 ica, p. 58. 1880) . In bogs and wet woods, widely distributed in the Northern 

 Hemisphere, in North America occurring from the Arctic regions south to the 

 northern part of the United States. 



