Raphiocarpus

Raphiocarpus

Full name and orig. publication: Raphiocarpus Chun, Sunyatsenia 6: 273 pl. 44 & fig. 32 (8 Nov. 1946).

Etymology: From the Greek ραφις, raphis = needle, and καρπος, karpos = fruit, alluding to the fruit, a very slender cylindrical capsule.

Synonym: Didissandra sect. Chiritoides K.Fritsch (1894).

Infrafamilial position: Didymocarpoideae-Trichosporeae-Didymocarpinae (Weber et al. 2013).

Description: Shrubs, subshrubs or perennial herbs, in R. sesquifolius with a distinct underground rhizome and annual shoots. Leaves opposite, the pairs well-spaced or tufted at the stem apex, the leaves of a pair equal or (partly strongly) unequal, petiole present or absent, lamina ovate or broadly lanceolate, base cuneate to cordate. Cymes axillary, 1- to several-flowered, flowers lax or dense. Sepals 5, free or connate. Corolla usually large, tube long, tubular to funnel-shaped and widening above, limb bilabiate, upper lip 2-lobed, lower lip 3-lobed, lobes rounded, coloration variable. Stamens 4, inserted near or above the middle of the corolla tube, included; anthers (?always) coherent, with divergent thecae, dehiscing by longitudinal slits; staminode present or lacking. Nectary ring-shaped. Ovary slender, unilocular; stigma entire or bilobed. Fruit an elongated capsule, dehiscing longitudinally into two valves.

Chromosome number: Unknown.

Species number: About 17 (Nguyen et al. 2023).

Type species: Raphiocarpus sinicus Chun.

Species names (only given in case of few species).

Distribution: S China (SW Sichuan, SE Yunnan, Guizhou, W, S & SE Guangxi, SW Guangdong, W Hubei) to N & C Vietnam.

Ecology: In montane regions, in shady and damp places under forests, on slopes near streams or in rock crevices.

Notes:
(1) The genus was originally described as monotypic with Raphiocarpus sinicus Chun (Chun 1946). The genus was then merged into Didissandra by W.T. Wang (1980). Examination of that genus (Weber & Burtt 1998a) showed that the Sino-Vietnamese species of Didissandra are not congeneric with the Malesian species. The latter comprise the type species, D. elongata C.B.Clarke, and had themselves to be split into two genera, Didissandra and Ridleyandra (Weber 1998a - c). With some hesitation, all the Sino-Vietnamese species of Didissandra were transferred to the reestablished genus Raphiocarpus, which was thus enlarged to comprise some 10 species.
(2) As presently understood, Raphiocarpus includes all species from China and Vietnam formerly placed in Didissandra as well as a number of new species described since. These (partly very ill-known) species do not form a homogeneous group and the genus may prove artificial, when the species (and adjacent genera) become better known.
(3) Vietnam holds presently 13 species. An annotated checklist and key to the Vietnamese species (with description of a new one) was published by Nguyen et al. (2023).
(4) Typical Raphiocarpus plants have a subshrubby habit, with lignescent shoots, iso- or weakly anisophyllous leaf pairs and indfundibuliform flowers with four stamens.
(5) Morphologically remarkable (and perhaps misplaced in Raphiocarpus) is R. sesquifolius (C.B.Clarke) B.L.Burtt. It has a horizontally growing underground rhizome from the end of which an aerial, annual stem arises. The stem bears a single, strongly anisophyllous leaf pair (the small leaf measuring at most one third of the length of the larger). One or few short-pedicelled flowers with a large blue and white-striped corolla arise from the axil of the larger leaf.

Selected references: Chun, Sunyatsenia 6(3-4): 271-304 (1946), Chinese Gesn.; Wang, Phytologia 45: 361-380 (1980), inclus. of Raphiocarpus in Didissandra; Weber & Burtt (a), Beitr. Biol. Pflanzen 70: 153-177 (1998, "1997"), re-establ., emend.; Weber & Burtt (b), ibid. 191-223; rev. Didissandra; Weber & Burtt (c), ibid. 225-273, rev. Ridleyandra; Chen et al., Plant Diversity and Resources 37(6): 727-732 (2015), new sp.; Middleton et al., Edinburgh J. Bot. 78, 365: 1-4 (2021), new sp.; Nguyen et al., PhytoKeys 218: 19-27 (2023), new sp.; Nguyen et al., Phytotaxa 616(3): 223-234 (2023), annot. checklist Vietnam, new sp.

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

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