4. Glyptostrobus Endlicher, Syn. Conif. 69. 1847.
水松属 shui song shu
Trees semievergreen, monoecious; winter buds small; branchlets dimorphic: perennial and annual; perennial branchlets remaining green for several years, with white lines of stomatal dots, becoming ridged and grooved with decurrent leaf bases; annual branchlets deciduous, short, never developing scars or buds. Leaves spirally arranged, sessile, trimorphic: leaves on main branches, perennial branchlets (after 1st year), and fertile branchlets radially spreading, scalelike, relatively thick (resembling leaves of Cupressus but spirally arranged), persistent for 2 or 3 years; leaves on annual branchlets of mature trees in 3 rows, radially spreading, subulate, quadrangular in cross section (resembling leaves of Cryptomeria), deciduous with branchlet as a unit; leaves of annual branchlets of young trees and seedlings often 2-ranked, sessile, linear, flat, thin, deciduous (resembling leaves of Taxodium). Pollen cones terminal on short, erect branchlets bearing scalelike leaves, solitary, ellipsoid; microsporophylls 15-20, spirally arranged, sessile; pollen sacs (2-)5-7(-9). Seed cones terminal, shortly pedunculate, erect when mature, ± pyriform; bracts of mature cones ± completely connate with cone scales (free only at apex), triangular, recurved, borne on central or middle distal part of abaxial side of cone scales; ovules 2 per bract axil; cone scales 20-22, spirally arranged, sessile, woody, basal scales sterile, median scales 2-seeded, with 6-10 triangular, acute teeth at distal margin, distal scales ligulate, multiangular, sterile. Seeds ellipsoid, slightly flattened, small, with a single, terminal, recurved wing. Cotyledons 4 or 5. Germination epigeal. 2n = 22*.
One species: China, extinct in the wild in N Vietnam.
A Tertiary relict species, the only surviving member of a genus formerly widespread prior to the Quaternary glaciations. Resembling the American genus Taxodium (which is introduced in China) in its vegetative characters, and occurring in similar habitats.