- 38 - 
Group i 
ia. Green cells of the branch-leaves in cross section with elliptic or oval cell- 
cavity, not exposed on either surface or slightly on the inner. 
2a. Hyaline cells bulging outward about pi their thickness, their walls 
smooth where applied to the green cells; (3) stem-leaves wide at apex. 
Sphagnum magellanicumP Brid. — Alaska to Calif.; eastern N. Amer. 
ia. Green cells of the branch-leaves in cross section lenticular to truncately 
elliptic, usually about equally exposed on both surfaces. 
2b. Hyaline cells bulging outward about pi their thickness, their walls smooth 
to densely papillose where applied to the green cells; (3) stem-leaves nar- 
row at apex. 
Sphagnum papillosum Lindb. — Alaska to Wash.; eastern N. Amer. 
(PI. XVII) 
ib. Green cells of the branch-leaves in cross section an isosceles-triangle narrower 
than equilateral, exposed on the inner surface only. 
2a. Hyaline cells bulging outward about pi their thickness, their walls smooth 
where applied to the green cells; (3) stem-leaves wide at apex. 
Sphagnum palustre L. 2 3 — Alaska to Calif.; eastern N. Amer. (PI. 
XVII) 
ib. Green cells of the branch-leaves in cross section an equilateral triangle, ex- 
posed on the inner surface only. 
2b. Hyaline cells bulging outward about their thickness, their walls strongly 
papillose to fibrillose where applied to the green cells; (3) stem-leaves 
rather narrow at apex. 
Sphagnum imbricatum Hornsch. 4 — Alaska; eastern N. Amer. (PL 
XVIII) 
Group 2 
ia. Branches in tufts of 6-12; hyaline cells of branch-leaves very finely papillose 
where applied to the green cells, bulging more on the outer than on the 
inner surface; (2) green cells of the branch-leaves in cross section with widest 
exposure on outer side, or equally on the 2 sides, (3) in cross section trun- 
cately elliptic; (4) hyaline cells of the branch-leaves bulging hardly at all 
on the inner surface, (5) with 1-8 pores on the outer surface and 1-4 on the 
inner. 
Sphagnum wulfianum Girg. — -Vancouver Island, B. C.; eastern N. 
Amer. (PI. XVIII) 
ib. Branches in tufts of 2-6; hyaline cells of the branch-leaves smooth where 
applied to the green cells, bulging more on the inner than on the outer 
surface. 
2 5. medium Limpr. ; S. intermedium Russ. 
3 5. cymbifolium Ehrh. ; also American specimens which have been referred to 5. turfaceum 
Warnst. 
4 5. austini Sull. 
