foc
《中国植物志》英文修订版
Flora of China
  FOC Vol.4 (1999)              | Family List  Taxodiaceae  PDF Taxodium  PDF   |  eFloras.org Link Font:+ Big | - Small
   5. Taxodium  Richard
落羽杉属   luo yu shan shu
  

  

Trees deciduous or semievergreen, monoecious; main branches persistent; lateral branches alternate and deciduous in winter; winter buds globose, small. Leaves spirally arranged, alternate, dimorphic: those on main branches persistent, inclined or curved upward and ± appressed to branchlets, subulate; those on annual branchlets deciduous together with branchlet as a unit, 2-ranked, linear or usually subulate. Pollen cones borne in long, pendulous, catkinlike racemes or panicles, ovoid; microsporophylls 6-many, spirally arranged; pollen sacs 4-9. Seed cones solitary, attached laterally by minute peduncle to apex of previous year’s growth, globose or ellipsoid but faceted; bracts and cone scales falling at maturity, spirally arranged; bracts attached to a conical axis, not overlapping, peltate, rhombic, each almost completely connate with its cone scale but with free, protruding, triangular, acute apex; ovules 2 per bract axil; cone scales shield-shaped, woody at maturity, apex irregularly quadrangular. Seeds 2 per cone scale, irregularly triquetrous, large, strongly keeled, wingless, water dispersed. Cotyledons 4-9. Germination epigeal. 2n = 22.

Two species: Guatemala, Mexico, United States; both introduced in China.

The number of distinct species of Taxodium is open to dispute: T. mucronatum might be better treated as a variety of T. distichum. The genus is similar in vegetative characters to Metasequoia, differing in its alternate (not opposite) branching and leaf arrangement. It also resembles Glyptostrobus, differing chiefly in its seeds which are strongly 3-angled and wingless (instead of 1-winged). Taxodium is now important in the afforestation of low lying river deltas with waterlogged soils, especially in SE China.

  
1Trees deciduous; leaves 10-15 mm, those on annual branchlets 2-ranked; pollen cones borne in crowded, short, dense racemes or panicles; seed cones dull, lacking glaucous bloom (but white powdery)1  Taxodium distichum    落羽杉
+Trees semievergreen or evergreen; leaves 7-11 mm, those on annual branchlets spirally arranged and scattered; pollen cones borne in long, slender, lax, spikelike panicles; seed cones glaucous2  Taxodium mucronatum    墨西哥落羽杉
   
   Lower Taxon
  • Taxodium distichum  (Linnaeus) Richard  落羽杉
  • Taxodium mucronatum  Tenore  墨西哥落羽杉
  • Taxodium distichum var. distichum    落羽杉 (原变种)
  • Taxodium distichum var. imbricatum  (Nuttall) Croom  池杉