The Families of Gymnosperms
Redwoods, Sequoia, Wellingtonia, Swamp Cypresses, Tasmanian Cedars.
Referred to Cupressaceae in recent treatments.
Vegetative. Evergreen, or deciduous (Taxodium, Metasequoia); trees (with parts mostly spirally arranged). Resinous (with resin cells but no canals in the wood, and canals in the stem cortex and leaves - cf. Cupressaceae). Main branches spiral (mainly), or whorled (more or less, in Cunninghamia only), or opposite (in Metasequoia only). The leafy branchlets flattened in one plane, or not flattened. The vegetative branch systems without conspicuously specialised short-shoots, or including highly specialised, leaf-bearing short-shoots (associated with phyllomorphs, e.g in Taxodium and Metasequoia). Mature leaves linear (or cultrate), or scale-like; when linear, acicular, or relatively soft; not clustered; alternate or alternate. Longitudinal resin canals present in the leaves; 1 per leaf, this median-abaxial, or in an abaxial arc.
Reproductive organization. Monoecious. The reproductive organization not flower-like. The ovules borne in female cones. The female cones woody. The seed-cone scales spirally arranged (nearly always), or opposite and decussate (Metasequoia); persistent, or deciduous, the cones disintegrating at maturity; woody. The ovules borne proximal-adaxially on the seed-cone scales. The bract-scales extensively fused to the seed-cone scales in mature cones (though almost free early in cone development), or not clearly resolvable from the seed-cone scales (e.g., in Cunninghamia and Taiwania, where according to Farjon and Garcia (2002) the "ovuliferous scale" vestiges are so reduced that the ovules are virtually borne on the bracts, cf. Cupressaceae sensu stricto). The seed-cone scales 2–7 ovuled. The ovules orthotropus (Taxodium, Cryptomeria), or anatropous.
Male cones with spirally arranged microsporophylls. Pollen-sacs 2–7 per microsporophyll, or 9 per microsporophyll (?). Pollen without air bladders. Pollination anemophilous, and involving a liquid drop mechanism although the grains lack air bladders.
Seeds and seedlings. Seeds winged.
Wood anatomy. Growth rings distinct. Heartwood present and distinctively coloured (often), or present but not distinctively coloured, or absent. Latewood not conspicuous (mostly), or conspicuous (e.g., Taxodium distichum). Wood with a distinct odour, or without distinct odour; with a distinct taste, or without distinct taste; greasy to the touch, or not greasy; without dimpled grain. Tracheids with opposite and multiseriate bordered pits, or with neither alternate nor opposite bordered pits; without callitroid pit-border thickenings. Margins of the tori not scalloped. Torus extensions conspicuously present (e.g., in Sequoia sempervirens), or absent. Earlywood tracheids without spiral thickenings. Axial parenchyma present. Axial parenchyma abundant, or scarce. Axial parenchyma zonate, or not zonate. Axial parenchyma with nodular thickenings or bead-like on the transverse or end-walls. Rays exclusively uniseriate, or not exclusively uniseriate (then usually only 1–2 cells wide?). Ray tracheids regularly present (Tsuga), or absent or very infrequent. Ray tracheids when present, not dentate. Earlywood ray cells with walls similar in thickness to those of adjacent vertical tracheids. Latewood ray cells with unpitted horizontal walls, or with pitted horizontal walls. The pitting when present, strong, or weak. Ray cells exhibiting indentures at the corners, or without indentures; without nodular thickenings on their end walls. Ray tissue without crystals. Earlywood cross-field pits cupressoid, or taxodioid, or cupressoid and taxodioid. Normal vertical resin ducts absent.
Geography, cytology. Temperate and sub-tropical; Eastern Asia, Tasmania and North America.
Basic chomosome number, n = 11.
Taxonomy. 14 species; Athrotaxis, Cryptomeria, Cunninghamia, Glyptostrobus, Metasequoia, Sequoia, Sequoiadendron, Taiwania, Taxodium. Order Coniferales.
Comments. The genera are mostly monotypic. For cone-scale morphology, see Farjon and Garcia, American Journal of Botany 2003;90:8–16.
Miscellaneous. • Athrotaxis cupressoides, A. laxifolia and A. selaginoides (Dallimore and Jackson). • Cryptomeria japonica (Dallimore and Jackson). • Cunninghamia lanceolata (Dallimore and Jackson). • Sequoia sempervirens (Dallimore and Jackson). • Sequoiadendron giganteum (Dallimore and Jackson). • Taxodium distichum (Dallimore and Jackson). • Taxodiaceae, Cephalotaxaceae and Cupressaceae: technical details (Sporne). • Cone-scale interpretation: Cryptomeria japonica (Florin). • Cone-scale interpretations: Sequoia, Sequoiadendron, Taxodium (Florin). • Cone-scale interpretation: Athrotaxis spp. (Florin). • Cone-scale interpretation: Cunninghamia lanceolata (Florin). • Leaf epidermes: Glyptostrobus, Metasequoia, Sequoia and Taxodium (Florin). • Wood anatomy: Sequoia sempervirens. • Wood anatomy: Taxodium distichum and Sequoia sempervirens.
To view the illustrations with detailed captions, go to the interactive key. This also offers full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, and distributions of character states within any set of taxa.
Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 2008 onwards. The families of gymnosperms. Version: 6th November 2009. http://delta-intkey.com’.