15. Thelypteris interrupta (Willdenow) K. Iwatsuki, Jap. J. Bot. 38: 314. 1963.
Hottentot fern, Willdenow's fern, spready tri-vein fern
Pteris interrupta Willdenow, Phytographia, 13. 1794; Cyclosorus gongylodes (Schkuhr) Link; C. interruptus (Willdenow) H. Itô; C. tottus (Thunberg) Pichi-Sermolli; Dryopteris gongylodes (Schkuhr) Kuntze; Thelypteris gongylodes (Schkuhr) Small; T. totta (Thunberg) Schelpe
Stems long-creeping, cordlike, 3--6 mm diam. Leaves monomorphic, evergreen, 3--6 cm apart, 50--150(--250) cm. Petiole straw-colored to tan, 20--125 cm × 3--6 mm, scaleless. Blade 30--125 cm, broadest at base, gradually narrowed distally to pinnatifid apex. Pinnae 7--30 × 1--2 cm, incised 1/3--1/2(--3/5) of width; segments deltate, rounded to acute; proximal pair of veins from adjacent segments united at acute or obtuse angle below sinus, with excurrent vein 2--4 mm. Indument abaxially of hairs 0.1--0.3 mm on costae and veins, or hairs often lacking, costae also with tan, ovate scales; veins, costules, and costae adaxially glabrous or sparsely pubescent; blade tissue without hairs on both sides, or hairy abaxially, usually with red to orange, shiny, sessile, hemispheric glands abaxially. Sori round, medial to supramedial; indusia tan, glabrous to hairy; sporangia with red- or orange-capped, stalked, globose glands arising from sporangial stalks. 2 n = 144.
Wet roadside ditches, riverbanks, marshes, and cypress swamps; 0--50 m; Fla., La.; Mexico; West Indies in the Antilles; Central America; South America to Argentina; tropical and subtropical Asia, Africa.
D. B. Lellinger (1985) applied the name Thelypteris interrupta to specimens from India, while using T . totta (type from South Africa) for North American and South American specimens. Diploid cytotypes are known from Africa and Asia, whereas all counts from the Neotropics are tetraploid. Until more counts are available and the morphologic variation (chiefly in glands, pubescence, and leaf size) in this species complex is better understood, I prefer to circumscribe the species broadly.
R. E. Holttum (1982) circumscribed Cyclosorus (as a genus) to include this species and one or two others.