Monographs Details: Calothrix tenella 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:Rivulariaceae
Description:Species Description - Filaments 60-90 µ long, mostly tortuous, 10-12 µ at the base, somewhat swollen above the base, tapering to a slender hair; trichome 4.8-6.2 µ at the base; cells quadrate to one-half as long as the diameter, homogeneous; pale aeruginous to yellowish green; heterocysts basal, spherical to subspherical, usually smaller than the trichome in diameter; sheath smooth, hyaline, thicker above the base.

Distribution and Ecology - Growing on and among Hepaticae on rocks, near Maricao, no. 1036 a, type.

Discussion:

PLATE 13, FIGURE 20

Calothrix epiphytica AY. & G. S. West is probably the nearest relative to the above species among all of the known species of the genus. C. tenella is a much shorter species with a more ample sheath.