Monographs Details: Tolypothrix penicillata var. brevis 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 1-2 mm. long, intermixed with other filamentous algae, main filaments 18 p diam., branches smaller; trichomes 12-14 µ diam.; cells cylindrical to slightly doliof orm, quadrate to 3 times as long; sheath thin, hyaline; heterocysts up to 50 µ long, cylindrical.

Distribution and Ecology - Growing among other filamentous algae and water plants, not forming a definite stratum alone, in a water reservoir at Eio Piedras, no. 118, type, and nos. Ill, 115, and 119 a; along the shore of Laguna Tortuguero, no. 843.

Discussion:The variety b re vis differs from the species in having shorter filaments with the diameter averaging greater and with the cells and heterocysts longer. No. 115 has mature cells averaging 38 to 45 ยต long in the older parts of the trichome.