Monographs Details: Nostoc membranaceum N.L.Gardner
Authority: Gardner, Nathaniel L. 1927. New Myxophyceae from Porto Rico. Mem. New York Bot. Gard. 7: 1-144. pl. 1-23.
Description:Species Description - Thallus in the juvenile stage more or less spherical and solid, soon becoming hollow, still later becoming much lacerated and expanding into thin, membranaceous, somewhat papery, strata 5-8 cm. across, 100-125 µ thick; trichomes tortuous, densly packed together; cells spherical to compressed-spherical, 4.6-5.2 µ diam., pale aeruginous, almost homogeneous, but at times containing a few small granules; heterocysts spherical, 5.8-6.4 µ diam., very numerous; tegument firm, smooth on the outside, hyaline or changin to yellowish brown with age; resting spores unknown.

Distribution and Ecology - Growing on sand rock along the shore of the Rio Grande, near Sabana Grande, no. 942, type; on a water pipe near a stream in the vicinity of Maricao, no. 1147.