Jerdonia

Full name and orig. publication: Jerdonia Wight, Icon. Pl. Ind. Orient. 4(2): 10, t. 1352 (Aug. 1848).

Etymology: Named for Surgeon-Major Thomas C. Jerdon, F.L.S. (1811-1872), a British physician, zoologist (specialised in birds) and botanist.

Synonyms: -

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

Description: (Sub)acaulescent rosette plants. Leaves long petiolate, lamina elliptic, reticulate. Pair-flowered cymes long-pedunculate (scapose), flowers few, bracteoles small. Sepals free, lanceolate. Corolla pale lilac with red lines; tube elongate, inflated above to form a distinct, reddish boss (pollination chamber) (not visible in the original drawings of Wight (1848); limb oblique, bilabiate, lobes ovate, obtuse. Stamens 4, filaments short, dilated upwards, two with distinct spurs; anthers connivent and apically coherent; thecae divergent, apically confluent. Nectary annular. Ovary ovoid, unilocular, with four parietal placentae; style slender; stigma small, obscurely bilobed. Fruit a broadly ovoid capsule, loculicidally dehiscent, bivalved. Seeds ellipsoid, testa striate-reticulate, with longitudinal furrows (slightly star-shaped in cross section).

Chromosome number: Unknown.

Type and only species: Jerdonia indica Wight.

Distribution: SW India (Nilghiri and Anamally Hills).

Ecology: On rocks in mountains.

Notes: The genus was described in Gesneriaceae by Wight (1848). However, it exhibits a number of anomalous features [e.g., isocotylous seedlings (Burtt 1977), filaments flat, two with a distinct appendage, unilocular ovary with four separate placentae (Wight 1848), seed anatomy (Weber 1989, Appendix to Charadrophila)] and its inclusion in Gesneriaceae has been doubted. Burtt (1963, 1977) pleaded for an accommodation in Scrophulariaceae. In Weber (2004) Jerdonia was listed under "Genera of uncertain familial affiliation". However, the presence of pair-flowered cymes (noted in Weber 1989) indicated strongly that the plant belongs to the family Gesneriaceae. The molecular data of Möller et al. (2009) provided definite evidence that Jerdonia must be placed in Gesneriaceae. Its position is near the base of the Didymocarpoid Gesneriaceae. In the classification of Weber et al. (2013) Jerdonia was placed in a monotypic subtribe of subfamily Didymocarpoideae tribe Trichosporeae.

Selected references: Burtt, Notes Roy. Bot. Gard. Edinburgh 24: 205-220 (1963); Burtt, Plant Syst. Evol., suppl. 1: 97-100 (1977), syst. pos.; Weber, Bot. Jahrb. Syst. 111: 115 (1989), Appendix to Charadrophila, characters; Weber in Kubitzki & Kadereit, Fam. Gen. Vasc, Plants, vol. 7: 63-158 (2004), Gesneriaceae; Möller et al., Amer. J. Bot. 96: 989-1010 (2009), mol. syst.; Weber et al., Selbyana 31(2): 68–94 (2013).

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

Page content and update responsibility/contact: Michael Möller.
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