Monographs Details: Phormidium durum N.L.Gardner
Authority: Gardner, Nathaniel L. 1927. New Myxophyceae from Porto Rico. Mem. New York Bot. Gard. 7: 1-144. pl. 1-23.
Family:Phormidiaceae
Description:Species Description - Filaments aggregated into a loose, floccose stratum, long, flexuous, rigid; trichomes 12-14 µ diam., neither constricted at the dissepiments nor attenuated at the apices; cells quadrate to 2 times as long as the diameter, homogeneous to finely granular when old, pale purplish-gray; cross-walls thin but very distinct; apical cell rounded, not capitate; sheath hyaline, changing to reddish brown when old, homogeneous, smooth, rigid, 2-3 µ diam.

Distribution and Ecology - Growing in flocculent masses among moss on shaded rock near the Hacienda Catalina, near Palmer, no. 746, type; on weathered rock near Humacao, no. 649. This latter collection seems to belong to the same species as no. 746 but is older and the sheath thicker.

Discussion:

PLATE 9, FIGURE 88

This species is characterized by the long, smooth, rigid filaments, due to the nature of the sheath. The sheath seems to persist for some time after the death and decay of the trichome.