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(Last Modified On 3/28/2013)
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(Last Modified On 3/28/2013)
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Genus
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Xylosma G. Foster
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PlaceOfPublication
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Fl. Ins. Austr. Prodr. 72, 1786, nom. gen. conserv.
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Synonym
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Myroxylon J. R. & G. Foster, Char. Gen. P1. 125, 1776, non L. f. (Suppl. 34, 233, 1781).
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Description
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Shrubs or small trees, often with axillary spines, the branchlets commonly lenticellate. Leaves alternate, sometimes borne in fascicles, usually short-petiolate, estipulate, the blade often ? coriaceous, usually glandular-dentate, penninerved, rarely entire-margined, without pellucid-glands. Inflorescences axillary, fasciculate or contracted-racemose, rarely racemose. Flowers small, dioecious or rarely polyga- mous; pedicels articulated above the base, the bracts minute; sepals 4-5(-6), imbri- cate, usually scale-like, slightly connate at the base, often ciliolate along the mar- gins, usually persistent; petals none; stamens oo (8-35 in Panamanian spp.), usually surrounded by an annular or glandular, fleshy disc, the filaments free, filiform, short- to usually long-exserted, the anthers minute, basifixed, extrose, longitudinally dehiscent; ovary sessile, inserted on an annular disc, 1-locular, with 2-3, rarely 4-6, parietal placentas, each placenta with 2, sometimes 4-6, ovules, the style entire or ? divided, sometimes very short, the stigmas scarcely dilated to dilated; rudi- mentary ovary wanting in male flowers. Fruits baccate, rather dry, indehiscent, surmounted by the persistent style, the pericarp rather thin-coriaceous, the seeds 2-8, + angular by mutual pressure, the testa thin; endosperm copious; embryo large, the coyledons broad.
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Habit
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Shrubs or small trees
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Distribution
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About 100 species throughout the tropics, but absent in Africa.
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Note
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In the absence of a comprehensive revision of the genus as a whole, it is impossible to give a satisfactory treatment of the genus in a regional flora. The specific delimitations within the genus are extremely difficult and neither the flowers nor the fruits yield good distinctive characters. All the keys in the regional tropical American floras are based mainly on vegetative characters, and I have been forced, alas, to do the same in this flora. It is consequently obvious that my treatment of Xylosma is only provisional. Nine species are listed in the following keys, four species without specific name. In view of the existing confusion within the genus I am reluctant to describe any new taxon and I leave the evaluation of the given characters of the unnamed species to the monographer-to-be of the genus! The bark contains tannin and the fruit is sometimes the source of dyestuff; the wood is moderately hard and rather heavy.
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Key
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a. Inflorescences fasciculate or contracted-racemose. b. Leaves, at least most of them, borne in fascicles at the end of very short pseudo-branches ................................ 1. X. anisophylla bb. Leaves not fasciculate. c. Leaves glabrous. d. Flowers dioecious. e. Stamens 16 or more (up to 35). f. Leaves usually broadly rounded at the apex, the margins with small, sometimes even inconspicuous, closely appressed, rounded serrations, their tips slightly overlapping the margin of the blade, the network of the venation inconspicuous on the upper surface; stamens ca 20-25; along the Atlantic Coast -.................................................................2. X. panamensis ff. Leaves obtuse to acute or long-acuminate, the margins distinctly crenate or serrate. g. Leaves commonly obtuse to acute at the apex, the net- work of the veins clearly noticeable on the upper sur- face when dry; stamens 16-20; style 2-3 lobed; Prov of Chiriqui, at 900-2250 m alt ................................... 3. X. flexuosa gg. Leaves long-acuminate at the apex, the network of the venation prominulous on both sides; stamens ca 35; style 4-5 lobed; Prov of Panama, lowlands .................... 6. Xylosma sp. 1 ee. Stamens 8-12; Prov of Cocle, at ca 500 m alt .................. 7. Xylosma sp. 2 dd. Flowers polygamous; Prov of Cocle, at sea level ............. 8. Xylosma sp. 3 cc. Leaves hispidulous or minutely hirtellous below. h. Branchlets and petioles densely short-hispid; leaf blades hispidulous below; petioles 2-4 mm long; Prov of Bocas del Toro, at sea level .................................... 4. X. hispidula hh. Branchlets and petioles inconspicuously puberulous; leaf blades minutely hirtellous below; petioles to 1 cm long or slightly longer; at 1800-2100 m alt ....................... 9. Xylosma sp. 4 aa. Inflorescences racemose ....................... 5. X. intermedia
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