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Published In: University of California Publications in Botany 6(4): 70. 1914. (Univ. Calif. Publ. Bot.) Name publication detailView in Biodiversity Heritage Library

Project Name Data (Last Modified On 9/15/2020)
Acceptance : Accepted
Note : Unplaced, perhaps Cinchonoideae, or possibly Ixoroideae
Project Data     (Last Modified On 9/15/2020)

Stylosiphonia is a monotypic genus that is only known from the type collection and may be extinct (Lorence et al., 2012). These plants are shrubs with medium-sized, thin-textured leaves, deciduous short triangular stipules, laxly cymose inflorescences borne at the stem ends and sometimes on short lateral branches, well developed showy 5-merous flowers that are apparently homostylous, narrow calyx lobes, slender well developed corollas with narrow lobes, and ellipsoid, septicidal capsules with angled seeds. The flowers are borne on quite well developed pedicels, and appear to be spreading if not deflexed in life. The overall form of the corolla resembles species of Faramea, but the color of the flowers is unknown. The capsules are borne on pedicels that are geniculate near the top, so the seeds would fall out of the top as it is pointed downward. Little else is known about this species. It has been actively sought by modern collectors in southern Mexico but not rediscovered. 

The relationships of Stylosiphonia are unclear. This genus was classified by Robbrecht (1988) in Rondeletieae, but that tribe at that time was circumscribed to include a systematically heterogeneous set of genera that are now classifed in several different tribes in two subfamilies, notably Condamineeae (Ixoroideae; Kainulainen et al., 2010) and Rondeletieae and Guettardeae (Cinchonoideae; Torres-Montúfar et al, 2020). Stylosiphona was excluded completely from Rondeletieae by them based on morphological analysis (2020: 26), but they were not able to clarify any other relationships for it because it has not been studied with molecular data. Its lack of raphides suggest that Stylosiphonia does not belong to Rubioideae, but beyond that its relationships are unclear. In any case, the second species that was provisionally included in Stylosiphonia is now included in Arachnothryx (which formerly was included in a a polyphletic circumscription of Rondeletia, adding to the confusion here).  

In general aspect Stylosiphonia resembles Deppea slendens (or perhaps this should be included Csapodya) in its thin-textured, similar leaves, lax cymose inflorescences, and pendulous flowers of similar size and form, but this other species differs in its 4-merous flowers, corolla lobes that are convolute in bud, 2-lobed stigma, and loculicidal capsules; it may also differ in its yellow to orange corollas, depending on the color of the corollas in Stylosiphonia.

Author: C.M. Taylor
The content of this web page was last revised in 15 September 2020.
Taylor web page: http://www.mobot.org/MOBOT/Research/curators/taylor.shtml

Distribution: Southern Mexico (Chiapas), but locality and habitat unknown. As discussed by Lorence et al. (2012), this species was probably collected in an area of evergreen forests at 700--2225 m, which supported a number of unusual endemic Rubiaceae but have since essentially all been destroyed; however, some other such species have been rediscovered through the heroic efforts of the botanical biodiversity team at the Herbario Eizi Matuda (HEM) in Chiapas and we can perhaps hope this one may be found again.


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Shrubs, unarmed, terrestrial, without raphides in the tissues. Leaves opposite petiolate, entire, with higher-order venation not lineolate, without domatia; stipules interpetiolar and shortly fused to petioles, triangular, cuspidate, arrangement in bud unknown, tardily deciduous. Inflorescences terminal and/or pseudoaxillary, cymose, several-flowered or flowers solitary, pedunculate, bracteate. Flowers pedicellate, bisexual, apparently homostylous, apaprently protandrous, perhaps diurnal; hypanthium ellipsoid to cupuliform; calyx limb developed, 5-lobed, lobes sometimes unequal, without calycophylls; corolla salverform with slender tube, internally glabrous, lobes 5, narrowly lanceolate, convolute in bud, without appendage; stamens 5, inserted in corolla tube, anthers narrowly oblong, dorsifixed, opening by linear slits, apparently without apical appendage, included; ovary 2-locular, with ovules several to numerous in each locule, perhaps axile placentas; stigma 1, claviform, included. Fruit capsular, ovoid, septicidally dehiscent from apex, coriaceous, smooth, with calyx limb deciduous; seeds numerous, angled, apparently small, rugulose.

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