A very distinct species, in size and habit resembling large forms of Sphagnum cymbifolium; agreeing also with that species in the scabrous dorsal apex of the leaf, and in the presence of spiral fibrillæ in the cortical cells of the stem and branches, a structure found in no other Sphagnum.
The principal characters separating this species from S. cymbifolium are the attenuated base of the branches; the fringed margin, suddenly contracted base, and different cross-section of the leaf; the absence of pores in the cortical cells of the stem, and their rare occurrence in those of the branches; and, especially, the peculiar form of the latter cells, which are suddenly bent or sagged in the middle, so that in cross-sections of the branch they give the appearance of being disposed in two or three layers, instead of one, as is really the case, as shown in fig. 7, sections being made at the dotted lines a b, c d, and e f.
A distinctive character is also seen in the large hyaline cells near the base of the branch-leaf, which, within and along that portion of their walls in contact with the small chlorophyllose cells, are beset with papillae or short spines (figures 11 and 12).
TAB 2.—Sphagnum Portoricense.
1. Planta naturali magnitudine.
2. Para caulis cum ramulorum fasciculo
3. Pars caulis transversim sectæ.
4. Folium caulinum.
5. Ramuli sectio transversalis.
6. Ramuli pars externa, cellularum corticalium formam lineis punctatis partim adumbrans.
7. Ejusdem sect, longitud. easdem cellulas in medio geniculatas monstrans.
8. Folium e ramuli medio desumptum.
9. Ejusdem apex a latere visa.
10. Ejusdem sectio transversalis.
11. Particula ejusdem sectionis, cellulas hyalinas intus papillosas exhibens.
12. Folii ramulini angulus basilaris, auriculas et cellulas hyalinas intus papillosas monstrans.
13. Cellulæ e folii ramulini media parte.
14. Eædem e parte superiore.
15. Folii particula emu cellulis partim dissolutis fimbriam formantibus.
