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Published In: Getreue Darstellung und Beschreibung der in der Arzneykunde Gebräuchlichen Gewächse 14: 555, sub t. 14 & 15. 1846. (Getreue Darstell. Gew.) Name publication detail
 

Project Name Data (Last Modified On 12/8/2022)
Acceptance : Accepted
Note : Tribe Dialypetalantheae
Project Data     (Last Modified On 3/19/2023)
Notes:

Rustia includes about 18 species of shrubs and small to large trees with robust leaves and inflorescences. The genus is unusual in Rubiaceae in several features. Overall Rustia is distinctive in its usually robust, oblanceolate to obovate leaves with punctate dots, deciduous stipules that are triangular and interpetiolar, terminal cymose inflorescences with well developed peduncles and lax axes; 5-merous flowers with a very short, usually truncate calyx limb, campanulate to tubular corollas with the lobes valvate or valvate-reduplicate in bud, exserted often thickened anthers with poridical dehiscence, and ellipsoid to obovoid loculicidal capsules with numerous small angled or winged seeds. Most Rustia species become quite large trees. The poricidal dehiscence of the anthers is very uncommon in Rubiaceae. The leaves apparently lack acarodomatia. Their pellucid punctations are rare in Rubiaceae, and a few plants appear to perhaps have bacterial nodules. This genus was studied and illustrated in detail by Delprete (1999), and one additional species was described by Will & Taylor (2010). Rustia occidentalis is perhaps the most commonly collected species.

Rustia shows a rather broad range of flower form and apparently pollination mode. Corolla color ranges from white to dull or perhaps bright red, and to green or yellowish green. The flowers were reported to be visited by hummingbirds, butterflies, and bees by Delprete (1999), and several species may be adapted for bat pollination. The anthers of some species are positioned in the mouth of the corolla, which has reduced lobes and is filled here by the anthers; Delprete (1999: 57) reported that these flowers are buzz-pollinted by bees. Corollas of Rustia range from white and 3-4 mm long in Rustia costaricensis, to 20-40 mm long and white, pink, green, greenish yellow, or red. The corolla is variously lobed for less than 1/4 of its length to almost completely. The flowers are held erect, spreading, or in some species pendulous. Delprete noted that in several species the inflorescence axes are held horizontally with the flowers all pendulous along them, and called this arrangement "secundiflorous". The flowers of several Rustia species are green to dull red and have a range of variation in color between plants and sometimes on the same plant (e.g., Rustia occidentalis). Delprete separated some species in part based on corolla color, but when the colors are not accurately noted or the plant is in fruit some of these species can be difficult to separate.

Delprete (1999) recognized two similar genera with poricidal anthers, Rustia and the monotypic genus Tresanthera, which he separated by anther form: opening by two apical pores in Rustia vs. by one lateral pore in Tresanthera. In at least some Rustia species, the "two apical pores" appear more like an apical slit that runs across the top of both of the thecae of the anther. He considered them closely related and classified them in the systematically complicated tribe Rondeletieae. In a molecular systematic study, Kainulainen et al. (2010; as Condamineeae) subsequently found Tresanthera nested within a clade otherwise composed of Rustia and synonymized them. Kainulainen et al. found Rustia to belong to their Tribe Dialypetalantheae, and related to Macrocnemum, Pentagonia, and Hippotis.

Several species of Rustia are similar to Dolichodelphys and Macbrideina, which lack pellucid glands in the leaves and have anthers that open by longitudinal slits; additionally Dolichodelphys has septicidal capsules and Macbrideina has large ligulate interpetiolar stipules that are held erect and flattened together in bud.

Author: C.M. Taylor
The content of this web page was last revised on 8 December 2022.
Taylor web page: http://www.mobot.org/MOBOT/Research/curators/taylor.shtml

Distribution: Wet and humid seasonal forest in southern Central America through northern Venezuela and Amazonian Peru, and disjunct in southern Brazil.
References:

 

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Shrubs and trees, unarmed, terrestrial, without raphides in the tissues. Leaves opposite, petiolate, with tertiary and quaternary venation not lineolate, without domatia, with pellucid punctations in the lamina; stipules deciduous, interpetiolar, triangular, imbricated in bud. Inflorescences terminal, cymose to thyrsiform, multiflowered and often quite large, pedunculate, bracteate. Flowers sessile to pedicellate, bisexual, homosylous, protandrous, often rather large and showy, fragrant, apparently diurnal; hypanthium ellipsoid to turbinate; calyx limb shortly developed, truncate, without calycophylls; corolla campanulate to tubular or salverform, white to yellowish green or dull red, internally glabrous to puberulous, lobes 5, triangular, in bud valvate or valvate-reduplicate, at least usually without appendage; stamens 5, inserted near base of corolla tube, anthers narrowly ellipsoid, dorsifixed, opening by terminal pores, partially to fully exserted, apparently without appendage; ovary 2-locular, ovules numerous in each locule, horizontal on axile placentas, stigmas 2-lobed, ellipsoid to linear, exserted. Fruit capsular, ellipsoid to obovoid and laterallly flattened, loculicidally dehiscent from apex, woody to chartaceous, lenticellate, with calyx limb persistent; seeds numerous, angled to fusiform, small (1--2 mm), sometimes with short wings, seed surface foveolate-reticulate, wings when present entire. 

 

Lower Taxa
 
 
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