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( Sequoia)
Sequoia sempervirens is the sole living species of the genus Sequoia in the cypress family Cupressaceae (formerly treated in Taxodiaceae). Common names include Coast Redwood and California Redwood (it is one of three species of trees known as redwoods, but "redwood" per se normally refers to this species). It is an evergreen, long-lived, monoecious tree living for up to 2,200 years, and this species includes the tallest trees on Earth, reaching up to 115.5 m (379.1 ft) in height and 8 m (26 ft) diameter at breast height. The name "sequoia" is sometimes used as a general term for the subfamily Sequoioideae in which this genus is classified, together with Sequoiadendron (Giant Sequoia) and Metasequoia (Dawn Redwood); as a common name, it usually refers to Sequoiadendron. Coast redwoods have a conical crown, with horizontal to slightly drooping branches. The bark is very thick, up to 30 cm (12 in), and quite soft, fibrous with a bright red-brown when freshly exposed (hence the name 'redwood'), weathering darker. The root system is composed of shallow, wide-spreading lateral roots. The leaves are variable, being 15-25 mm long and flat on young trees and shaded shoots in the lower crown of old trees, and scale-like, 5-10 mm long on shoots in full sun in the upper crown of older trees; there is a full range of transition between the two extremes. They are dark green above, and with two blue-white stomatal bands below. Leaf arrangement is spiral, but the larger shade leaves are twisted at the base to lie in a flat plane for maximum light capture. The seed cones are ovoid, 15-32 mm long, with 15-25 spirally arranged scales; pollination is in late winter with maturation about 8-9 months after. Each cone scale bears 3-7 seeds, each seed 3-4 mm long and 0.5 mm broad, with two wings 1 mm wide. The seeds are released when the cone scales dry out and open at maturity. The pollen cones are oval, 4-6 mm long. The species is monoecious, with pollen and seed cones on the same plant. Its genetic makeup is unusual among conifers, being a hexaploid (6n) and likely autoallopolyploid (AAAABB). The mitochondrial genome is (unlike other conifers) paternally inherited (Neale et al. 1989). Coast Redwoods occupy a narrow strip of land approximately 750 km (470 miles) in length and 8-75 km (5-47 miles) in width along the Pacific coast of North America; the elevation range is mostly from 30-750 m, occasionally down to sea level and up to 920 m (about 3,000 feet) (Farjon 2005). They usually grow in the mountains where there is more precipitation from the incoming moisture off the ocean. The tallest and oldest trees are found in deep valleys and gullies, where year-round streams can flow, and fog drip is regular. The trees above the fog layer, above about 700 m, are shorter and smaller due to the drier, windier, and colder conditions. In addition, tanoak, pine and Douglas-fir often crowd out redwoods at these elevations. Few redwoods grow close to the ocean, due to intense salt spray, sand and wind.
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