Diastema

Full name and orig. publication: Diastema Benth., Bot. Voyage Sulphur 132 (14 Apr. 1845, “1844”), non Diastema L.f. ex Jackson (1912).

Etymology: From the Greek διαστημα, diastēma = space, interval, referring to the separated (not coherent) anthers. 

Synonyms: Diastemma Lindl. (1847), Diastemation Walp. (1858), nom. superfl. & illeg., Diastemella Oerst. (1861).

Infrafamilial position: Gesnerioid Gesneriaceae (Gesnerioideae) - Gloxinieae.

Description: Slender, terrestrial, perennial herbs with scaly rhizomes. Stem short, unbranched, hirsute or villous. Leaves opposite, ± isophyllous, usually with long petioles; lamina membraneous, crenate, dentate, or serrate. Inflorescence usually a terminal, bracteose raceme. Sepals free, often spreading. Corolla white, sometimes with purple markings on the lobes, tubular or funnelform, only slightly broader toward the limb, neither spurred nor ventricose; limb of rounded lobes, regular or slightly zygomorphic. Stamens 4; filaments adnate to base of corolla tube; anthers orbicular, at first apically coherent, later free, thecae slender, dehiscent by slits above. Nectary of 5 glands of equal length, sometimes connate into 2-3 glands. Ovary semi-inferior; style slender; stigma bilobed. Fruit an obovoid, membraneous, 2-valved capsule, with apex convex.

Chromosome number: 2n = 26.

Species number: Over 20.

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

Type species: Diastema racemiferum Benth.

Distribution: Bolivia to Mexico, Venezuela, centre of diversity in Andean Colombia, Equador and Peru.

Ecology: Terrestrial herbs growing on damp rocks near streams, in wet forests at low elevations.

Notes: The genus is a very natural assemblage of species, apparently without a close affinity to the other genera of the Gloxinieae.

Selected references: Wiehler, Selbyana 6: 170 (1983); Skog, Ann. Missouri Bot. Gard. 65: 891-896 (1979), reg. rev. (Panama); Feuillet & Steyermark, Fl. Venezuel. Guayana 5 (1999), reg. rev.; Skog, Monogr. Syst. Bot. Missouri Bot. Gard. 85: 1114-1128 (2001), reg. rev. (Nicaragua).

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

Illustrations:

Diastema racemiferum Benth., type species

Left: Skog, Ann. Missouri Bot. Garden 65, fig. 15 (1979)
Right: cult. Smithsonian Institution, origin Ecuador (coll. J. Clark), phot. J.K. Boggan

Diastema comiferum (DC.) Benth. ex Walp.

Left: phot. R. Myhr
Right: cult. Smithsonian Institution, origin Peru, phot. J.K. Boggan

Diastema  vexans H.E.Moore

Cult. Smithsonian Institution, origin probably Columbia, phot. J.K. Boggan

 


last modified: 2007-01-05