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Published In: Publications of the Field Museum of Natural History, Botanical Series 8(3): 153. 1930. (Publ. Field Mus. Nat. Hist., Bot. Ser.) Name publication detailView in Biodiversity Heritage Library
 

Project Name Data (Last Modified On 9/15/2021)
Acceptance : Accepted
Note : Tribe Hamelieae
Project Data     (Last Modified On 11/10/2021)
Notes :

Syringantha includes one species found in a a relatively northern range and dry habitat for Neotropical Rubiaceae. These plants are slender shrubs and small trees with medium-sized to rather small, perhaps rather fleshy leaves, interpetiolar triangular stipules, terminal cymose inflorescences, medium-sized 5-merous flowers, tubular corollas with quite short imbricate lobes, and ellipsoid, woody, septicidal capsules that contain numerous winged seeds. The tissues contain raphides. The stipules are cadcuous. The inflorescences are dichasially to irregularly branched, with the ultimate axes often "secundiflorous" or monochasial. The corollas in bud have a narrow ridge or wing extending along their tube portion and connecting with the midrib of the lobes. The corollas at anthesis are bright yellow and about 1.5--2 cm long.As for most Rubiaceae genera with imbricate aestivation, the corolla lobes here are quincuncial (i.e., with two lobes external). The capsules are about 5--8 mm long, and smooth and not lenticellate. The seeds are about 3--4 mm long with an elliptic central body and a prolonged narrow wing on each end. Relatively little is not known about this species or its ecology; based on its habitat, it likely is deciduous. 

Morphologically, Syringantha is recognizable by a suite of characters but its relationships are not well shown by any of them. Its single species was long confused with Exostema, which is quite similar in stipule, leaf, and flower and fruit characters, although it differs from Exostema in its raphides. The morphology and separation of Syringantha from Exostema were studied, detailed, and illustrated by McDowell (1996), who noted that this genus agrees with Hamelieae overall but its woody capsules and numerous flattened winged seeds are unusual within this tribe. McDowell detailed the filaments as flattened and connivent, but Borhidi (2012: 534) described these as fiiiform, which suggests he found them to be rounded. Syringantha is also similar in aspect to Chiococca grandiflora

Borhidi (2012) recognized two varieties of Syringantha coulteri based on leaf shape and whether the "cenbtral flower of the dichasium" is sessile or pedicellate. These varieties were described by him as having overlapping ranges. The leaf forms he distinguished for these, "narrowly elliptic to rhombic" vs. "oblong to linear-lanceolate", are not entirely clear as to their exact differences, and the inflorescences are often irregularly branched so it is difficult to identify which is the terminal flower of a dichasium, or "the" dichasium, here. McDowell (1996) noted that the flowers vary from having a well developed pedicel to subsessile, with a pedicel 0.5 mm long, and this latter condition is sometimes considered sessile by some authors so this distinction is also difficult to entirely clarify. 

Syringantha is similar in aspect and a number of morphological details to Machaonia pringlei, which has schizocarpous fruits with one seed in each mericarp. 

Author: C.M. Taylor
The content of this web page was last revised on 13 July 2021.
Taylor web page: http://www.mobot.org/MOBOT/Research/curators/taylor.shtml

Distribution : Dry sclerophyllous thorn-scrub, matorral, and pink-oak vegetation at 900-2000 m, central to northeastern Mexico (Guanajuato, Hidalgo, Querétaro, Tamaulipas).
References :

 

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Shrubs and small trees, slender, unarmed, terrestrial, with raphides in the tissues. Leaves opposite, petiolate, entire, with the higher-order venation not lineolate, without pubescent domatia; stipules interpetiolar, triangular, erect and perhaps valvate in bud, caducous. Inflorescences terminal, cymose with axes often monochasial, mutiflowered, pedunculate, bracteate. Flowers pedicellate, bisexual, homostylous, apparently protandrous, medium-sized, perhaps fragrant, apparently diurnal; hypanthium turbinate; calyx limb developed, deeply 5-lobed, without calycophylls; corolla tubular, in bud 5-winged to -ridged, yellow, glabrous inside, lobes 5, triangular, short, imbricated (quincuncial) in bud, erect at anthesis, without appendages; stamens 5, inserted near base of corolla tube, filaments flattened and connivent (i.e., forming a false tube), anthers narrowly oblong, basifixed, dehiscent by linear slits, partially exserted, with apiculate appendage at base and top; ovary 2-locular, with ovules numerous in each locule, on axile placentas, stigma 1, clavate, partially exserted. Fruit capsular, ellipsoid, septicidally dehiscent from apex with valves apparently remaining fused at base, woody, smooth, without lenticels, with calyx limb persistent, with disk portion enlarging to up to 20% of length of capsule; seeds ca. 12 per locule, flattened, medium-sizezd (3--4 mm), fusiform, marginally winged, entire, with wing prolonged and narrowly triangular on each end. 

 
 
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