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(Last Modified On 1/17/2013)
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(Last Modified On 1/17/2013)
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Genus
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ALNUS Gaertn.
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PlaceOfPublication
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Fruct. & Sem. 2:54. 1791.
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Synonym
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Alnaster Spach, in Ann. Sc. Nat. Ser. II. 15:200. 1841. Clethropsis Spach, loc. cit. 201. 1841. Semidopsis Zumaglini, Fl. Pedem. 1:249. 1849. Duschekia Opiz, Seznam. 3 8. 18 5 2. Alnobetula Schur, in Verh. Siebenb. Ver. Naturw. 4:68. 1858.
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Description
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Terminal buds present; stipules caducous. Staminate catkins borne at the end of last year's leaf shoot; cymules 3-flowered (often reduced at distal portion of catkin), subtended by a primary bract, 2 secondary bracts and each lateral flower by a single abaxial bract (rarely an adaxial bract develops); tepals 0-6; stamens 4(-6), adnate to the tepals. Pistillate catkins borne on few-leaved dwarf-shoots or borne in a leaf axil subtending the staminate catkin, often several lateral catkins develop to form a raceme, each cymule composed of 2 lateral flowers, the bracts as in staminate cymules; perianth reduced to !small glands which are sometimes adnate to the ovary; the catkin at maturity resembling a small cone; ovary 2- or 3-carpellate. Fruit a nut more or less winged. The presence of polymerous flowers in the same cymule is not unusual. Hermaphroditic flowers are sometimes found toward the base of the catkin (either staminate or pistillate).
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Distribution
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Species approximately 20, only 1 in Panama.
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