Trachystigma

Etymology: Composed of the Greek τραχνς, trachys = hispid, and στιγμα, stigma = stigma, alluding to the papillose-hispid stigma. 

Synonyms: Roettlera Vahl sect. Trachystigma (C.B.Clarke) Fritsch (1895).

Infrafamilial position: Didymocarpoid Gesneriaceae - "AAfrican and Madagascan genera" (Weber 2004).

Description: Herb of the habit of Acanthonema or a unifoliate Streptocarpus. Leaf (macrocotyledon) cordate-ovate, sessile. Cymes emerging in a series from the leaf base, pedunculate, several- to many-flowered. Sepals nearly free to base, narrow-lanceolate. Corolla rather short-tubed, widening towards the mouth, limb slightly bilabiate, lobes rounded. Fertile stamens 2, scarcely exserted; filaments with an apical tooth; anthers with divergent thecae, coherent. Staminode 1, filiform. Nectary unilateral, oblique. Ovary cylindrical, unilocular; style as long as ovary; stigma bilobed. Fruit a slender, cylindrical capsule, opening along the median line of the upper carpel only.

Chromosome number: Unknown.

Type and only species: Trachystigma mannii C.B.Clarke

Species names (incl. publication and synonyms): See Skog, L.E. & J.K. Boggan. 2005: World checklist of Gesneriaceae: http://persoon.si.edu/Gesneriaceae/Checklist.

Distribution: Tropical W Africa (Gabon, perhaps also S Cameroun).

Notes: The genus is apparently closely allied to Acanthonema, differing mainly by (a) the cylindrical ovary developing to a capsule of c. 3 cm length, (b) the larger corolla with wide mouth, (c) the larger and more branched inflorescences. Trachystigma can be distinguished at once from a unifoliate Streptocarpus by the straight (not twisted) capsule, the toothed filaments and the unilateral nectary.

Selected references: Baker & Clarke, Fl. trop. Africa 4: 503 (1906); Burtt, Fl. Cameroun 27: 24 (1984), reg. rev.; Burtt, Fl. Gabon 27: 15-16 (1985), reg. rev.; Weigend & Edwards, Bot. Jahrb. Syst. 118: 59-80 (1986), palyn.

Bibliography: See Skog, L.E. & J.K. Boggan. 2005. Bibliography of the Gesneriaceae. 2^nd edition: http://persoon.si.edu/Gesneriaceae/Bibliography.

Illustrations:

Trachystigma mannii C.B.Clarke, type and only species C.B.Clarke, in A. & C. DC., Monogr. phan. 5/1, t. 14 (1883)

last modified: 2007-07-13