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(Last Modified On 12/18/2012)
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(Last Modified On 12/18/2012)
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Family
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COMBRETACEAE
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Contributor
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A. W. EXELL
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Description
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Trees, shrubs or lianas, rarely subherbaceous (never in Panama). Leaves opposite, verticillate, alternate or spiral, exstipulate, simple, almost always entire. Flowers perfect or perfect and staminate in the same inflorescence, usually actino- morphic, sometimes slightly zygomorphic, in axillary or extra-axillary, elongated or subcapitate spikes or racemes or in terminal and sometimes axillary panicles. Receptacle (hypanthium) usually in two distinct parts, the lower receptacle sur- rounding the ovary and adnate to it and the upper receptacle (calyx-tube) pro- duced beyond it to form a short or long tube terminating in the (sometimes poorly developed) calyx-lobes, caducous or persistent. Calyx-lobes 4-5 (rarely 6-8 or almost obsolete) sometimes accrescent (not in Panama genera). Petals 4-5 or absent, conspicuous or very small. Stamens usually twice as many as the sepals or petals, borne inside the upper receptacle, usually in two series, exserted or included, anthers versatile or more rarely adnate to the filaments and immobile. Disk usually present, often hairy, intrastaminal. Style free in American genera (partly attached to the upper receptacle in Quisqualis). Ovary completely inferior in all American genera (semi-inferior in the West African genus Strephonema), unilocular, with usually 2 (sometimes up to about 6) pendulous ovules of which only one usually develops. Fruit (pseudocarp) very variable in size and shape, fleshy or dry, usually indehiscent, often variously winged or ridged, 1-seeded.
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Habit
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Trees shrubs
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Habit
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ianas herb
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Note
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The Combretaceae, an entirely tropical and subtropical family, found in rain- forest, deciduous forest, savanna and mangrove formations, comprise 18 genera of which two, Combretum and Terminalia, contain the great majority of species. Some species of Terminalia yield useful timber and the 'myrobalans' used for dye- ing in Asia. A few species of Combretum are cultivated in the tropics and as stove-plants in temperate countries. Terininalia catappa L., a native of tropical Asia and Polynesia, is often planted in towns as an avenue tree and Quisqualis indica L., the Rangoon Creeper, is a climber often grown in tropical gardens. In the course of their evolution the Combretaceae seem to have developed under the influence of two principal tendencies: (1) the attraction of pollinating insects by the massing of relatively small flowers in dense or rather dense inflorescences, though with a number in individual exceptions (such as Combretum cacoucia); (2) dispersal of the fruits by means of laterally extended wings (again with numer- ous exceptions). The progressive development of inflorescences and fruits along these lines leads to obvious space difficulties as the more the flowers are crowded into pseudo-capitate spikes the less room there is for the development of wings to the fruits. Several of the genera recognized in the family represent different solu- tions to this problem. In Panama we have one of the most 'advanced' solutions in the genus Conocarpus where the flattened pseudocarps, perhaps after a secondary reduction in the wings, are tightly packed into a cone-like aggregate fruit. The fact that isolated species of Combretum, belonging to quite different sections, have wingless or nearly wingless fruits, often distributed by water, may also indicate that wingless fruits have developed from winged ones. In the various forms which the winging of the fruit may take we have an interesting combination of two factors. From the inferior ovary, probably origi- nating from a single carpel, embedded in receptacular tissue, there is apparently what we might call an 'internal' tendency to produce a 2-winged fruit resulting from the bilateral symmetry of the carpel. From the 4-merous or 5-merous calyx, on the other hand, there seems to be an 'external' tendency to produce a 4-winged (Combretum) or 5-winged (Combretumn and Terminalia) fruit. In Terminalia, in particular, it is interesting to see the effect of these two tendencies. We find, for example, in addition to numerous species with either 2-winged or 5-winged fruits respectively, certain species, such as T. amiazonia in Panama, with primarily 2-winged fruits in which three secondary wings or ridges are also developed. If this interpretation is correct it would seem that the great plasticity in the winging of the fruit is due to the surrounding, in an inferior fruit, of a bilateral 'core' by a 4-merous or 5-merous 'skin'.
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Key
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a. Receptacle (hypanthium) without adnate bracteoles; petals present or absent. b. Petals present (in Panama species) ......................................................... 1. COMBRETUM bb. Petals absent. c. Fruits solitary, not closely aggregated. d. Anthers versatile. e. Calyx-lobes triangular; upper receptacle and calyx caducous (in Panama species) before the fruit ripens ............................... 2. TERMINALIA ee. Calyx only slightly toothed; upper receptacle and calyx per- sistent on the fruit or only tardily dehiscent ............................... 3. BUCIDA dd. Anthers adnate to the filaments, immobile ................................... 4. BUCHENAVIA cc. Fruits aggregated into a cone-like structure ------------------------------------- 5. CONOCARPUS aa. Receptacle (hypanthium) with two small adnate bracteoles near the apex; petals present ............. .......................................................................... 6. LAGUNCUL ARIA
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Note
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The introduced genus Quisqualis (receptacle without adnate bracteoles; petals present) is separated from Coinbreturn by the adnation of the style for part of its length to the wall of the upper receptacle (calyx-tube). The species cultivated, Q. indica, can at once be distinguished from all the indigenous Combretaceae by its much elongated, narrowly infundibuliform upper receptacle (calyx-tube), up to 8 cm. long when the flowers are fully developed.
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