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Published In: Annals of the Missouri Botanical Garden 27(3): 344. 1940. (25 Sept 1940) (Ann. Missouri Bot. Gard.) Name publication detailView in BotanicusView in Biodiversity Heritage Library
 

Project Name Data (Last Modified On 6/24/2021)
Acceptance : Accepted
Note : Tribe Guettardeae
Project Data     (Last Modified On 9/15/2020)
Notes:

This genus includes two species of trees found in humid forests in northern Central America and southern Mexico. These species can grow to a large size, and are characterized by interpetiolar, triangular, usually deciduous stipules, rather robust leaves, multiflowered, usually whitened inflorescences borne at the stem apices, small pedicellate 4-merous flowers, and unusual flattened samara-like fruits. These species have been reviewed and classified by various authors, but are actually not well known morphologically. The floral biology was reported as distylous in Allenanthus erythrocarpus by Lorence et al. (2012), but not specified there for Allenanthus hondurensis and suggested in the genus description there to perhaps be homostylous; the flowers of Allenanthus erythrocarpus studied here appear to also be homostylous, and the genus is characterized thusly here. Similarly, the arrangement of the corolla lobes in bud has been variously reported as valvate or thinly imbricated based on herbarium specimens, but apparently not checked with field observations. The fruits are rather small, 4-8 mm long, and obovoid with usually a truncate to retuse apex. These are borne on well developed pedicels and have papery wings and a thickened, often spongy central portion, and are often flushed with pink. The fruits appear to disperse often as a single fruit, but at least sometimes separate tardily into two segments. Allenanthus is not commonly collected and so often overlooked. This genus was long characterized as a Central American group, but has recently been discovered by the intrepid plant explorers of the Medellín Botanical Garden in the humid, seasonal forests of the lower Magdalena Valley in northern Colombia.

The most complete modern review of this genus is the treatment by Lorence in Lorence et al. (2012), who recognized two species of Allenanthus, and two varieties of one of them that are distinguished morphologically by size of the leaf blade and are disjunct geographically. Borhidi (2004) presented a different classification of these plants, with Allenanthus synonymized with Machaonia and its two long-recognized species treated by him as one species with three varieties. These two genera share indehiscent to schizocarpous dry fruits with the characters of Guettardeae that have a single ovule per locule (Taylor, 2010), but Machaonia is separated here by its slender shrub habit, corollas lobes with clearly imbricated aestivation, unwinged ellipsoid fruits, and habitat in dry forest and scrub. Allenanthus, Machaonia, and Neoblakea were noted to be similar morphologically by Taylor (2010), and found grouped together on a well suported clade in the majority rule molecular phylogram of Manns & Bremer (2010). They found some species of all three of these genera grouped on one lineage within this clade and two other species of Machaonia grouped on another of its lineages, but did not regard their results as adequate to evaluate the status of the genera in their analysis. Torres-Montúfar et al. (2020) included Machaonia but not Allenanthus or Neoblakea in their study of Guettardeae.

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

Distribution: Humid to seasonal broadleaf forests and pine-oak forests at 50-1100 m, southern Mexico to northern Colombia.
References:

 

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Trees to 30 m tall, unarmed, terrestrial, without raphides in the tissues. Leaves opposite, petiolate, entire, with the higher-order venation not lineolate, sometimes with pubescent domatia; stipules interpetiolar, triangular, erect and valvate in bud, caducous to persistent. Inflorescences terminal and in axils of uppermost leaves, thyrsiflorm or paniculiform to corymbiform, mutiflowered, pedunculate, bracteate. Flowers pedicellate, bisexual, homostylous, protandrous, small, perhaps fragrant, apparently diurnal; hypanthium obconic to obovoid; calyx limb developed, 4-lobed, without calycophylls; corolla salverform, white to cream, rather small (2.5-3 mm long), pubescent inside, lobes 4, triangular, valvate or perhaps thinly mbricated in bud, without appendage; stamens 4, inserted in upper part of corolla tube, anthers narrowly oblong, dorsifixed, dehiscent by linear slits, exserted, without appendage; ovary 2-locular, with ovules 1 per locule, apical and pendulous, stigma 2, linear to ellipsoid, exserted. Fruit samaroid, dry, papery to spongy, obovoid, flattened, indehiscent or tardily with 2 valves, with calyx limb persistent; seeds 1 per locule, obconic, laterally flattened.

 
 
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