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cotyledonous

Pinaceae

The family Pinaceae (pine family), is in the order Pinales and includes many of the well-known conifers of commercial importance such as cedars, firs, hemlocks, larches, pines and spruces. It is the largest conifer family in species diversity, with between 220-250 species (depending on taxonomic opinion) in 11 genera, and the second-largest (after Cupressaceae) in geographical range, found in most of the Northern Hemisphere with the majority of the species in temperate climates but ranging from subarctic to tropical. One species just crosses the equator in southeast Asia. Major centres of diversity are found in the mountains of southwest China, Mexico, central Japan and California.

They are trees (rarely shrubs) growing from 2 to 100 m tall, mostly evergreen (except Larix and Pseudolarix, deciduous), resinous, monoecious, with subopposite or whorled branches, and spirally arranged, linear (needle-like) leaves. The female cones are large and usually woody, 2-60 cm long, with numerous spirally-arranged scales, and two winged seeds on each scale. The male cones are small, 0.5-6 cm long, and fall soon after pollination; pollen dispersal is by wind. Seed dispersal is mostly by wind, but some species have large seeds with reduced wings, and are dispersed by birds. The embryos are multi-cotyledonous, with 3-24 cotyledons.

Classification

The 11 genera are divided into four subfamilies, based on the cone, seed and leaf morphology:

  1. Cones biennial, rarely triennial, with each year's scale growth distinct, forming an umbo on each scale. Cone scale base broad, concealing the seeds fully from abaxial view. Seed without resin vesicles. Seed wing holding the seed in a pair of claws. Leaves with primary stomatal bands adaxial (above the xylem) or equally on both surfaces. Subfamily Pinoideae (Pinus)
  2. Cones annual, without a distinct umbo. Cone scale base broad, concealing the seeds fully from abaxial view. Seed without resin vesicles, blackish. Seed wing holding the seed loosely in a cup. Leaves with primary stomatal bands adaxial (above the xylem) or equally on both surfaces. Subfamily Piceoideae (Picea)
  3. Cones annual, without a distinct umbo. Cone scale base broad, concealing the seeds fully from abaxial view. Seed without resin vesicles, whitish. Seed wing holding the seed tightly in a cup. Leaves with primary stomatal bands abaxial (below the phloem vessels) only. Subfamily Laricoideae (Larix, Cathaya, Pseudotsuga)
  4. Cones annual, without a distinct umbo. Cone scale base narrow, with the seeds partly visible in abaxial view. Seed with resin vesicles. Seed wing holding the seed tightly in a cup. Leaves with primary stomatal bands abaxial (below the phloem vessels) only. Subfamily Abietoideae (Abies, Cedrus, Pseudolarix, Keteleeria, Nothotsuga, Tsuga)

References

  • Farjon, A. 1998. World Checklist and Bibliography of Conifers. Royal Botanic Gardens, Kew. 300 p. ISBN 1-900347-54-7.

External links

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