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(Last Modified On 11/13/2012)
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(Last Modified On 11/13/2012)
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Genus
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MARATHRUM Humb. & Bonpl.
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PlaceOfPublication
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PI. Aequinox. 1:40-41, tab. II. 1808.
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Synonym
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Lacis Mart. Nov. Gen. & Sp. 1:6. 1824.
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Description
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Small to medium-sized stemless herbs known to be attached to roots in only a few species, the sterile plants often larger and coarser than the fertile, with an irregular, sometimes branched, adhesive base. Leaves either distichous or inserted along the margin of the thalloid base, repeatedly pinnate with all the pinnae alter- nate or slightly opposite, or entire with a few lobes along the margin; petiole sometimes fleshy, often dilated at the base. Flowers at first enclosed in a persistent, membranaceous spathe which splits irregularly at the tip, 1 to many, solitary or fascicled between the leaf-bases; pedicel scarcely enlarged at the tip in some species, in others abruptly enlarged; tepals 3-25 in a complete or incomplete whorl, in- conspicuous, squamiform to filiform, inserted on the margin of the receptacle in species with enlarged pedicels, but sometimes inserted at different levels in species with normal or scarcely enlarged pedicels; stamens 2-25, in a complete or incom- plete whorl (the latter unknown in Panamanian species), rarely united at the base, the filaments lanceolate, 3-angled at the base, sometimes branched, nerved, the anthers sagittate, introrse; pollen ellipsoidal to subglobose, 3-sulcate; ovary 2- celled, ellipsoidal, attenuate at the base, with 2 equal carpels, 8-ribbed; placenta of the same shape as the ovary, with many ovules; styles 2, filiform or cylindric, cohering at the base or very rarely free, often emarginate. Fruit with 2 equal, persistent, 5-ribbed valves.
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Distribution
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Central America, Antilles, northwestern South America.
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Key
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a. Pedicels not thickened at the tip; leaves 3-5 times pinnate. b. Stamens one-third to one-half as long as the ovary; pollen ellipsoidal, 17 X 14 microns ............................................ .. ........ 1. M. STENOCARPUM bb. Stamens about as long as the ovary. c. Tepals 0.5-1.0 mm. long; styles 2-3 mm. long; pollen ellipsoid, 16 X 13 microns .............. ......... 2. M. OXYCARPUM cc. Tepals 0.5 mm. long or shorter; styles 0.5-2.0 mm. long. d. Leaves shorter than 3 cm., usually some dilated and cuneately fasciate-flabelliform; pollen subglobose, 15 X 14 microns.. . 3. M. PUSILLUM dd. Leaves 0.5-20 cm. long, of essentially similar form throughout. e. Ultimate leaf-divisions filiform or nearly so. f. Leaf rachis not winged, transparent when young; pollen narrowly ellipsoid, 20 X 11 microns; styles 0.5-1.0 mm. long 4. M. LEPTOPHYLLUM ff. Leaf rachis distinctly winged, not transparent when young; pollen ovoid, 16 X 14 microns; styles 1.0-2.0 mm. long 5. M. INDIFFERENS ee. Ultimate leaf-divisions usually round to spathulate or tri- angular, not filiform. f. Leaf rachis narrowly winged; ovary 2.5-3.0 mm. long; pollen subglobose, 15 X 14 microns ... .. ... 6. M. CHEIRIFERUM ff. Leaf rachis not winged; ovary 3.5-4.0 mm. long; pollen ellipsoid, 17 X 14 microns ... M. ALLENII aa. Pedicels thickened at the tip; leaves repeatedly bifurcate ................... 8. M. FOENICULACEUM
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