Note: The variant spelling Hormothamnion was initiated by Bornet & Flahault (1888 [1886–1888]: 259) and has been used by most subsequent authors. Komárek & Anagnostidis (1989: 312, 316) placed Hormothamnium in the synonymy of Hydrocoryne Schwabe (in Sprengel, 1827: 314, 373; Schwabe ex Bornet & Flahault, 1887 [1886–1888]: 128) with a query. According to these authors, the two genera perhaps may be distinguished by the type of akinete formation, but this process must be reinvestigated. Hormothamnium enteromorphoides, the type of the generic name, was formally transferred to Hydrocoryne by Umezaki & Watanabe (1994b: 305).
Hormothamnium enteromorphoides Grunow, 1867: 31, pl. I: fig. 25 (type locality: Guadeloupe, West Indies).—Jadin, 1894: CLXVII.— Forti, 1907: 486–487.— Reinbold, 1907: 552.— Geitler, 1932 [1930–1932]: 677, fig. 436.— Iyengar & Desikachary, 1944: 52, fig. 13.— Desikachary, 1959: 433, pl. 61: figs. 6–8.— Sigee, 1966: 68.— Tsuda & Newhouse, 1966: 94.— Isaac, 1971: 2.— Hackett, 1977: 11.— Lawson, 1980: 19.— Thajuddin & G. Subramanian, 1992a: table III.
INDIAN OCEAN DISTRIBUTION: India, Kenya, Maldives, Mauritius, Tanzania.
Note: Drouet (1978: 165, 195), after examining the holotype of this species (in W), assigned it to Anabaina oscillarioides Bory de Saint-Vincent.