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Didymochlamys Hook.f. (Rubiaceae: not assigned to subfamily or tribe)

Charlotte M. Taylor [webpage]
Missouri Botanical Garden
P.O. Box 299
St. Louis, MO 63166

Click on the images below to see a larger image

Didymochlamys whitei in western Colombia

Fruits
Fruits

Flowers
Flowers

Didymochlamys Hook.f. includes 2 species of small, usually epiphytic herbs found in northern South America and southern Central America. These plants grow on boulders and tree trunks in wet forests, and are often overlooked as Rubiaceae. Their leaves are distichous and opposite but strongly anisophyllous, and may appear alternate if not examined carefully. The interpetiolar stipules of Didymochlamys are quite small and quickly caducous, so that the smaller leaf of the anisophyllous pair may be mistaken for a stipule, and Didymochlamys is therefore sometimes confused with Gesneriaceae.

The inflorescences of Didymochlamys are distinctive, with a short fascicle of 2-5 flowers enclosed in two complanate enlarged green bracts (the genus name refers to these bracts). The relatively small flowers are white often tinged with blue or violet, and their lobes have the margins crisped to incised or appendaged. The cupuliform fruits are berrylike at least in their early stages, although those of D. connellii are reportedly later dehiscent though at the apex (whether this dehiscence is loculicidal or septicidal is unreported). The numerous seeds are small and bear a tuft of silky trichomes at one end, similarly to the seeds of Hillia Jacq.

The relationships of Didymochlamys within the Rubiaceae are not yet clear, and this genus has never been studied in any detail. Steyermark (1967) did review this genus, but quite briefly. Steyermark (1974) presented a floristic treatment for D. connellii in Venezuela and an illustration [1974(1): p. 428, fig. 70]. Dwyer (1980) presented a floristic treatment of D. whitei in Panama and illustration (1980: p. 148, fig. 33), but incorrectly called the Panamanian plants "D. connellii".

Key to the Species of Didymochlamys

1. Larger leaves 2-4 x 0.4-1 cm; peduncles 1-3 mm long; inflorescence bracts
elliptic to ovate, 1-1.5 x 0.5-1 cm; calyx lobes 2-2.5 mm long; corolla tubes 12-14 mm long; corolla lobes 3-4.5 mm long, subentire or with two elongated appendages... D. connellii

1. Larger leaves 3-7.5 x 0.5-1.4 cm; peduncles 5-25 mm long; inflorescences
bracts ovate, 1-2 x 1-2 cm; calyx lobes 4-5 mm long; corolla tubes 13-14 mm long; corolla lobes 1.5-2 mm long, the margins irregularly incised to appendaged throughout, the appendages up to 2 mm long...D. whitei

References

  • Dwyer, J.D. 1980. Part IX. Family 179. Rubiaceae. In: R.E. Woodson, Jr. & R.W. Schery, Flora of Panama. Ann. Missouri Bot. Gard. 67: 1-522.
  • Steyermark, J.A. 1967. Didymochlamys. In: B. Maguire & Collaborators, The botany of the Guayana Highland-Part VII. Mem. New York Bot. Gard. 17: 290-291.
  • Steyermark, J.A. 1974. Rubiaceae. In: T. Lasser, Flora de Venezuela 9(1-3): 1-2070.
  • Taylor, C.M. 2001. Rubiaceae. In: W.D. Stevens et al., Flora de Nicaragua. Monogr. Syst. Bot. Missouri Bot. Gard. 85(3): 2206-2284.

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List of Names and Synonyms of Hillia

Further information on these names can be found in the TROPICOS database [http://www.tropicos.org/].

Didymochlamys connellii N.E. Brown, southeastern Venezuela to Guyana,

350-1100 m
Didymochlamys whitei Hook.f., southern Nicaragua to western Colombia,
100-1000 m

Text and Images, unless otherwise indicated, Copyright © by Charlotte M. Taylor. All rights reserved.

This page was revised on April 8, 2008.

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