Trees or rarely shrubs, evergreen or deciduous, monoecious. Branchlets often dimorphic: long branchlets with clearly spirally arranged, sometimes scalelike leaves; short branchlets often reduced to slow growing lateral spurs bearing dense clusters of leaves at apex. Leaves solitary or in bundles of (1 or)2-5(-8) when basally subtended by a leaf sheath; leaf blade linear or needlelike, not decurrent. Cones unisexual. Pollen cones solitary or clustered, with numerous spirally arranged microsporophylls; microsporophyll with 2 microsporangia; pollen usually 2-saccate (nonsaccate in Cedrus, Larix, Pseudotsuga, and most species of Tsuga). Seed cones erect or pendulous, maturing in 1st, 2nd, or occasionally 3rd year, dehiscent or occasionally indehiscent, with many spirally arranged ovulate scales and bracts; ovulate scales usually smaller than bracts at pollination, with 2 upright ovules adaxially, free or only basally adnate with bracts, maturing into seed scales. Seed scales appressed, woody or leathery, variable in shape and size, with 2 seeds adaxially, persistent or deciduous after cone maturity. Bracts free or adnate basally with seed scales, well developed or rudimentary, exserted or included. Seeds terminally winged (except in some species of Pinus). Cotyledons 2-18. Germination hypogeal or epigeal. 2n = 24* (almost always).
Trees (occasionally shrubs), evergreen (annually deciduous in Larix ), resinous and aromatic, monoecious. Bark smooth to scaly or furrowed. Lateral branches well developed and similar to leading (long) shoots or reduced to well-defined short (spur) shoots ( Pinus , Larix ); twigs terete, sometimes clothed by persistent primary leaves or leaf bases; longest internodes less than 1cm; buds conspicuous. Roots fibrous to woody, unspecialized. Leaves (needles) simple, shed singly (except whole fascicles shed in Pinus ), alternate and spirally arranged but sometimes proximally twisted so as to appear 1- or 2-ranked, or fascicled, linear to needlelike, sessile to short-petiolate; foliage leaves either borne singly (spirally) on long shoots or in tufts (fascicles) on short shoots; juvenile leaves (when present) borne on long shoots, scalelike; resin canals present. Pollen cones maturing and shed annually, solitary or clustered, axillary, ovoid to ellipsoid or cylindric; sporophylls overlapping, bearing 2 abaxial microsporangia (pollen sacs); pollen spheric, 2-winged, less commonly with wings reduced to frill (in Tsuga sect. Tsuga ), or not winged (in Larix and Pseudotsuga ). Seed cones maturing and shed in 1--3 seasons or long-persistent, sometimes serotinous (not opening upon maturity but much later: Pinus ), compound, axillary, solitary or grouped; scales overlapping, free from subtending included or exserted bracts for most of length, spirally arranged, strongly flattened, at maturity relatively thin to strongly thickened and woody (in Pinus ), with 2 inverted, adaxial ovules. Seeds 2 per scale, elongate terminal wing partially decurrent on seed body (wing short or absent in some species of Pinus ); aril lacking; cotyledons 2--12[--18].
Burns, R.M. and B.H. Honkala. 1990. Silvics of North America. 1.Conifers. Washington. [Agric. Handb. 654.] Canadian Forestry Service. 1983. Reproduction of conifers. Forest. Techn. Pub. Canad. Forest. Serv. 31. Farjon,A. 1990. A Bibliography of Conifers. Königstein. [Regnum Veg. 122.] Hosie, R.C. 1969. Native Trees of Canada, ed. 7. Ottawa. Pp. 83--95. Little, E. L. Jr. 1979. Checklist of United States Trees (Native and Naturalized). Washington. Pp. 33--36. [Agric. Handb. 541.] Silba,J. 1986. Encyclopaedia Coniferae. Phytologia Mem. 8: 1--127.