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(Last Modified On 1/14/2013)
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(Last Modified On 1/14/2013)
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Family
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LORANTHACEAE
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Contributor
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CARLOS TOLEDO RIZZINI
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Description
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Vines, undershrubs, shrubs or rarely trees, always parasitic on roots or stems; the vines, less commonly the shrubs, bearing adventitious roots united with their hosts. Leaves usually opposite, sometimes alternate, entire, seldom reduced to scales, more or less coriaceous and inconspicuously nerved, the nervation either palmate or pinnate; without stipules. Flowers very large to minute, frequently showy because of the bright colors, androgynous or unisexual, spicate, clustered, strobilate or arranged in ternations, these in racemes, spikes, corymbs, umbels and so on, rarely solitary, subtended by bractlets either free or coalescent, or bractless; perianth simple or double; calyculus present or absent; tepals (perianth segments) 3-6 or none; stamens as many as the tepals, reduced to staminodia in the pistillate flowers, the filaments joined to the tepals; pollen grains variable, globose or tri- angular, the exine either smooth or granulose (in some small genera it is reticulate or aculeate); ovary formed by the receptacle or blossom axis (thus the above mentioned calyculus is the edge of the receptacle), l- (rarely several) -celled, sterile and poorly developed in the staminate flowers; stigma capitate, wanting in the male flowers which, however, have a slightly reduced style. Fruit (indeed a pseudofruit since it is developed from the receptacle), so far as American species are concerned, a berry (a drupe in certain Old World forms), frequently showing a milky layer containing rubber and persistent perianth parts; seed solitary, naked, the endosperm obviously developed and fleshy, rarely lacking; embryo small, with 2 rather large cotyledons.
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Habit
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Vines shrubs
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Habit
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rarely trees
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Note
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The plants of this family are either completely (when they are leafless and without chlorophyll) or partly (when they bear normal foliage leaves) parasitic on other woody plants. The roots applied to the host become haustoria and through these part or all the food supply is secured from the latter. The few erect, terrestrial, tree-like forms live upon roots and their haustoria are underground. The family comprises about 38 genera and 1,400 species, mainly tropical and subtropical but occasionally found in temperate regions. It is very homogeneous, yet the morphological types are well marked so that the New World forms are readily distinguishable from the Old World ones. The Central American species are more closely related to the South American than to the North American or West Indian ones.
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Key
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a. Flowers small to very large, at least 2 mm. long, not immersed in the rachis of the inflorescence. b. Plants terrestrial. Bractlets large, foliaceous, free. -1. GAIADENDRON bb. Plants growing upon others. Bractlets minute, mostly coalescent. c. Flowers very small, hidden inside short, long-bracted spikes, the male flowers naked. Pollen grains spherical, prominently aculeate. 2. ANTIDAPHNE cc. Flowers perianthed, freely inserted, conspicuous. Pollen grains neither round nor aculeate. d. Flowers several cm. long, showy, each subtended by a cupula or cup. Endosperm wanting -------------------- 3. PSITTACANTHUS dd. Flowers up to 1 cm. long, usually shorter, without a cup below the calyculus. Endosperm present. e. Flower perfect, each subtended by one bract plus two bract- lets, all closely united. - 4. PHRYGILANTHUS ee. Flowers unisexual (the vestigial pistil remains in the staminate flowers as the pollenless anthers do in the pistillate ones), each set of bract and bractlets subtending three flowers (ternation). f. Filaments of the stamens slender and thin. Pollen grains dimorphous: the fertile triangular and tricolpate mixed with sterile, globose and smooth ones .-------------------------- 5. STRUTHANTHUS ff. Filaments of the longer stamens scalloped at each side. Pollen grains belonging to one type, triangular. . 6. PHTHIRUSA aa. Flowers very small, no longer than 2 mm., sunken in depressions in the rachis of the spike. b. Calyculus distinct though poorly developed. Tepals 6. Pollen grains reticulate ----------------------.----------------------------------------------------- 7. ORYCTANTHUS bb. Calyculus lacking. Tepals 3. Pollen grains smooth. c. Anther 1-celled, dehiscing transversely .---------------------------------------------- 8. DENDROPHTHORA cc. Anther 2-celled, opening by 2 longitudinal slits.. . 9. PHORADENDRON
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