Tetracentron
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| Tetracentron sinense Oliv. |
Tetracentron sinense is a flowering plant, the sole species in the genus Tetracentron. It is also often considered the sole species in the family Tetracentraceae, though some botanists include it in the family Trochodendraceae together with the very distinct genus Trochodendron.
It is native to southern China and the eastern Himalaya, where it grows at altitudes of 1100-3500 m in a temperate climate; it has no widely used common name in English, though is sometimes called "spur-leaf".
It is a tree growing to 20-40 m tall. The leaves are deciduous (the Flora of China reporting it as evergreen is an error), borne singly at the apex of short spur shoots, each leaf dark green, broad heart-shaped, 5-13 cm long and 4-10 cm broad, with a rugose surface and a serrated margin. The spur shoots bear a one leaf each year, slowly lengthening with each subsequent year.
The flowers are inconspicuous, yellowish green, without petals, produced on slender catkins 10-15 cm long; each flower is 1-2 mm diameter. The fruit is a follicle 2-5 mm diameter, containing 4-6 seeds.
Tetracentron shares with Trochodendron the feature, very unusual in angiosperms, of lacking vessel elements in its wood. This has long been considered a very primitive character, resulting in the classification of these two genera in a basal position in the angiosperms; however, genetic research by the Angiosperm Phylogeny Group has shown it to be in a less basal position (early in the eudicots), suggesting the absence of vessel elements is a secondarily evolved character, not a primitive one.
