Monographs Details: Phormidium calidum var. olivaceum 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 scattered among other algae, not forming a definite stratum, relatively short, flexuous, 7-8 µ diam; trichomes 5.8-6.8 µ diam., straight at the apices and not attenuated, or 1-2 apical cells slightly attenuated and uncinate, capitate, frequently interrupted in the sheath; cells quadrate to one-third diam. long, homogeneous, dark olive-green or grayish green; sheath very thin, smooth, homogeneous, hyaline.

Distribution and Ecology - Growing on rocks among Hepaticae, and in association with other algae, about seven kilometers east of Coamo, no. 1870 e, type.

Discussion:The above-diagnosed variety of P. calidum Gomont may be distinguished by the interrupted character of the trichome, which in some specimens is broken into numerous parts which gravitate some distance from each other, by the darker color, and by the less pronounced capitate apical cells.