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(Last Modified On 3/20/2013)
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(Last Modified On 3/20/2013)
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Genus
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Chamaesyce S. F. Gray
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PlaceOfPublication
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Nat. Arr. Brit. PI. 2: 260, 1821.
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Synonym
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Anisophyllum Haworth, Syn. PI. Succ. 1959, 1812, non Jacquin (Sel. Stirp. Amer. Hist. 283, t. 180, fig. 45, 1763). Euphorbia sect. Anisophyllum Roeper in Duby, A.P. D.C., Bot. Gall. ed 2, 1: 412, 1828.
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Description
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Herbs or subshrubs, annual or short perennating, prostrate to ascending or erect, milky latex in all parts; monoecious; the main axis aborting, the secondary axes few to many, rarely rooting at nodes. Leaves opposite, simple; petiolate with stipules interpetiolar, distinct or joined; blades expanded, with chlorophyll-bearing cells mainly in a sheath around veins and colorless areas in between, the base inequilateral, the margin entire or serrate. Cyathia terminal but appearing axil- lary, solitary at nodes or clustered in cymules; lobes 5 approximating glands; glands 4 or with fifth vestigial, alternating with lobes, with petaloid appendages (these rarely obsolete). Staminate flowers few to many; naked; monandrous; pol- len grains subglobose, tectate, 3-colporate. Pistillate flowers terminal, solitary; naked; ovary 3-celled each with a single ovule, the styles 3, free or joined basally, partly bifid. Fruit capsular, almost always fully exerted and not splitting cyathium at maturity; seed ovoid, angled or terete, the coat smooth or variously sculptured, ecarunculate.
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Habit
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Herbs or subshrubs
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Note
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Plants of disturbed habitats, most abundant in rather dry situations and suc- cumbing quickly to competition in more favorable sites. A genus of about 250 species, of world-wide distribution but with by far the largest number of species in the New World. The genus is poorly represented in Panama by comparison with neighbouring countries, and of the 10 species found six are known from five or fewer collections of each.
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Reference
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Wheeler, L. C., Eupjhorbia subgenus Chamaesyce in Canada and the United States exclusive of Canada. Rhodora 43: 97-154, 168-205, 223-286, 1941 (Re- printed as Contr. Gray Herb., Harvard Univ. 136). Burch, D. G., Two new species of Chamaesyce (Euphorbiaceae), new com- binations, and a key to the Caribbean members of the genus. Ann. Missouri Bot. Gard. 53: 90-99, 1966.
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Key
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a. Capsule pubescent, at least when young. b. Plant erect or ascending; cyathia in short-stalked leafy dichasia 1. C. lasiocarpa bb. Plant prostrate or decumbent; cyathia in glomerules or on condensed leafy laterals. c. Cyathia borne in dense lateral and terminal leafless glomerules - 2. C. hirta cc. Cyathia borne on condensed leafy laterals. d. Capsule not fully exserted, splitting cyathium at maturity; glands subcircular, appendages usually all equal in size - 3. C. thymifolia dd. Capsule fully exserted and not splitting cyathium at maturity; glands rimming cyathium, appendages unequal in size with one pair very long and often concealing capsule. e. Glandular appendages pubescent on underside - 4. C. densiflora ee. Glandular appendages glabrous on underside - 5. C. dioica aa. Capsule glabrous. f. Leaf margins entire. g. Plants prostrate to decumbent; stipules distinct, deeply lanciniate -- - --. 6. C. ammannioides gg. Plants erect to sprawling; stipules united, short-cleft or fringed - 7. C. buxifolia ff. Leaf margins serrate, at least in upper 1/3. h. Capsule more than 2 mm long; seed to 1.8 mm long - 8. C. bahiensis hh. Capsule less than 2 mm long; seed rarely longer than 1 mm. i. Cyathia in almost leafless lateral and terminal glomerules; capsule subspherical, less than 1.4 mm long - 9. C. hypericifolia ii. Cyathia in leafy lateral and terminal dichasia; capsule oblong-ovoid, more than 1.6 mm long - 10. C. hyssopifolia
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Note
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Three other common weeds of the American tropics are to be expected in Panama: C. ophthalmica (Pers.) Burch is like a delicate plant of C. hirta, but may be distinguished by the position of its glomerules of cyathia which are al- ways terminal; C. prostrata (Ait.) Small and C. serpens (H.B.K.) Small are each small prostrate plants. The first is easily distinguished by its capsule, stiff-hairy only on the angles, and the second by its joined, scale-like white stipules and the fact that it frequently roots at the nodes.
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