[Trachystigma]

 Important notes

The genus Trachystigma is presently not accepted. It has been included in Streptocarpus (sensu Nishii et al. 2015) and attributed to subg. Streptocarpella sect. Trachystigma by Nishii et al., Taxon 64(6): 1243-1274, 2015).

The name of the species mentioned and/or illustrated below now reads: Streptocarpus mannii (C.B.Clarke) Mich.Möller & Nishii.

Trachystigma (in its traditional sense)

Trachystigma mannii C.B.Clarke, type and only species

C.B.Clarke, in A. & C. DC., Monogr. phan. 5/1, t. 14 (1883)

Full name and orig. publication: Trachystigma C.B.Clarke, in A. & C.DC., Monogr. phan. 5/1: 131 (July 1883).

Etymology: Composed of the Greek τραχνς, trakhys = rough, asperous, rugose, and στíγμα, stigma = stigma, alluding to the papillose-hispid stigma.

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

Infrafamilial position: Didymocarpoid Gesneriaceae - "African 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

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.

Tax. details, cytology, and bibliography: Gesneriaceae Resource Centre (GRC). Royal Botanic Garden Edinburgh.