12 SPHAGNACEAE 



2 — Chlorophyll cells of the branch leaves entirely included, or exposed 



about equally on both surfaces 3 



Chlorophyll cells of the branch leaves usually triangular in section, 



with the base exposed on the inner surface of the leaf 4 



3 — Chlorophyll cells of the branch leaves exposed about equally on both 



surfaces, with a central lumen papillosum 



Chlorophyll cells of the branch leaves short-elliptic in section, central 



and usually entirely included magellanicum 



4 — Chlorophyll cells of the branch leaves usually isosceles-triangular in 



section palustre 



Chlorophyll cells of the branch leaves equilateral-triangular in sec- 

 tion: 5 



5 — Cortical cells of the branches with their bases plane or nearly so. 



imbricatum 

 Cortical cells of the branches each communicating by a saccate to funnel- 

 shaped extension with the next cell underneath portoricense 



6 — Cortical cells of the branches uniform, each with a pore at the upper 



end 7 



Cortical cells of the branches of two kinds, the larger retort cells with 

 a neck and a pore in the axils of the leaves; or, if uniform, with- 

 out pores 8 



7 — Chlorophyll cells of the branch leaves included compactum 



Chlorophyll cells of the branch leaves exposed on the outer surface. 



strictum 

 8 — Stem leaves with the membrane of the hyaline cells mostly resorbed 

 on the outer surface, on the inner with membrane-gaps only in the 



apical cells 9 



Stem leaves with the membrane of the hyaline cells usually not 

 greatly resorbed on the outer surface, or if so, resorbed on both 



surfaces, producing a very lacerate leaf apex 10 



9 — Plant large; branch leaves ovate-hastate, mostly squarrose. .squarrosum 

 Plant smaller; branch leaves ovate-lanceolate, usually imbricate .. teres 

 10 — Chlorophyll cells of the branch leaves exposed exclusively or more 

 broadly on the outer surface; or, if with central lumen and ap- 

 proximately equal exposure, the pigment brown 11 



Chlorophyll cells of the branch leaves exposed exclusively or more 

 broadly on the inner surface; or, if with central lumen and ap- 

 proximately equal exposure, the pigment red 18 



11 — Cortical cells of the stem small, thick- walled 12 



Cortical cells of the stem larger, thin-walled, in 1-3 layers 13 



12 — Chlorophyll cells of the branch leaves isosceles-triangular in section, 



the apex of the triangle reaching the inner surface of the leaf . recurvum 

 Chlorophyll cells of the branch leaves equilateral-triangular in sec- 

 tion, the apex of the triangle not reaching the inner surface of 



the leaf pulchrum 



13 — Chlorophyll cells of the branch leaves broadly triangular in section, 



exposed only on the outer surface tenellum 



