Monographs Details: Porphyrosiphon robustus 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 - Filaments closely intertwined, forming a loose floccose stratum, of moderate length, 30-36 µ diam.; trichomes not constricted, neither attenuated nor capitate, 16-20 µ diam.; cells onethird to one-half as long as the diameter, homogeneous, bright aeruginous, cross-walls very distinct; apical cell rounded, wall not thickened; sheath rigid, at first hyaline, homogeneous, later changing to pale rose-pink and becoming decidedly lamellose, the ends usually extending much beyond the trichomes, and becoming collapsed and more or less lacerated.

Distribution and Ecology - Growing on rocks among moss, etc., about four kilometers north of Utuado, no. 1570, type; on red soil at Hacienda Holm, Mayagiiez, no. 1185 a.

Discussion:PLATE 9, FIGURE 83