The Families of Gymnosperms
Monkey Puzzles, Norfolk Island Pine, Kauri, Candelabra Tree.
Vegetative. Evergreen (in some, the leaves remain green for up to fifteen years); trees. Resinous (with resin canals in stem medullary rays and cortex, and in the leaves). Main branches whorled. The leafy branchlets not flattened. Mature leaves broad and flat (often broad-based, with many parallel veins), or linear; acicular, or relatively soft (mostly); not clustered; alternate (although the main branches are usually whorled). Longitudinal resin canals present in the leaves.
Reproductive organization. Monoecious (Agathis, usually), or dioecious (Araucaria). The ovules borne in female cones. The female cones woody (almost spherical). The seed-cone scales spirally arranged; deciduous, the cones disintegrating at maturity (the seed either shed attached to the cone scale, with the latter serving as wings, or detaching from the cone scale along with a wing); 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 in Araucaria the tip is conspicuously free, constituting a ligule). The seed-cone scales 1 ovuled. The ovules anatropous.
Male cones elongate, the microsporophylls with 5–15 abaxial pollen-sacs in Agathis, 8–15 in Araucaria. The pollen grains produce numerous prothallial cells. Pollen-sacs 5–15 per microsporophyll. Pollen without air bladders. Pollination anemophilous, with fertilization involving lodgement of the grain on the cone-scale (or in Araucaria on the ligule), and growth of the pollen tube to the ovule via a nucellar beak projecting through the micropyle (i.e., no liquid drop mechanism).
Seeds and seedlings. Seeds winged. Cotyledons 2(–4).
Wood anatomy. Growth rings indistict. Heartwood present and distinctively coloured (usually, though often weakly developed), or present but not distinctively coloured, or absent (Araucaria cunninghamii). Latewood not conspicuous. Wood without distinct odour; with a distinct taste (Agathis australis), or without distinct taste (usually); not greasy; without dimpled grain. Tracheids with alternate bordered pits; without callitroid pit-border thickenings. Earlywood tracheids without spiral thickenings. Axial parenchyma absent. Ray tracheids absent or very infrequent. Earlywood ray cells with horizontal walls thinner than those of the adjacent vertical tracheids above and below the ray. Latewood ray cells with unpitted horizontal walls. Ray cells without indentures; without nodular thickenings on their end walls. Ray tissue without crystals. Earlywood cross-field pits cupressoid (or araucarioid), or piceoid and cupressoid (Araucaria cunninghamii). Normal vertical resin ducts absent.
Geography, cytology. Temperate to tropical; Southern hemisphere, excluding Africa.
Basic chomosome number, n = 13.
Taxonomy. 40 species; Agathis, Araucaria, Wollemia. Order Coniferales.
Miscellaneous. • Auraucaria heterophylla, habit. • Araucaria heterophylla, cone details. • Agathis and Araucaria: technical details (Sporne). • Cone-scale interpretations of Araucaria spp. (Florin). • Agathis australis, Araucaria bidwillii, Araucaria heterophylla (Dallimore and Jackson). • Leaf epidermis: Agathis alba (Florin). • Wood anatomy: Agathis vitiensis.
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’.