Sweetgum

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Sweetgum (Liquidambar) is a genus of four species of flowering plants in the family Altingiaceae, though formerly often treated in the Hamamelidaceae. They are all large, deciduous trees, 25-40 m tall, with palmately lobed leaves arranged spirally on the stems. The flowers are small, produced in a dense globular inflorescence 1-2 cm diameter, pendulous on a 3-7 cm stem. The fruit is a woody multiple capsule 2-4 cm diameter (popularly called a "gumball"), containing numerous seeds.

Species

Liquidambar acalycina - Chang's Sweetgum (central & southern China)
Liquidambar formosana - Chinese Sweetgum (central & southern China, southern Korea, Taiwan, Laos, northern Vietnam).
Liquidambar orientalis - Oriental Sweetgum (southwest Turkey, Greece: Rhodes).
Liquidambar styraciflua - American Sweetgum (eastern North America from New York to Texas and also eastern Mexico to Guatemala).

The genus was much more widespread in the Tertiary, but has disappeared from Europe due to extensive glaciation in the north and the Alps, which has served as a blockade against southward migration. It has also disappeared from western North America due to climate change, and also from the unglaciated (but nowadays too cold) Russian Far East. There are several fossil species of Liquidambar, showing its relict status today.

Uses

They are popular ornamental trees, particularly in warm-temperate areas with hot summers, being some of the most reliable trees for good autumn (fall) colours in these conditions.

The trees yield a gum known as storax, used in herbal medicine. This gum contains a small amount of the aromatic hydrocarbon styrene; the styrene extracted from Liquidambar orientalis gum resulted in the discovery in 1839 of the first known polymer polystyrene.

Image:Liquidambar (copalme d amerique).jpg|Liquidambar styraciflua Image:Koeh-089.jpg|19th century illustration of Oriental Sweetgum (Liquidambar orientalis)

References and external links

Hsu, E. & Andews, S. (2005). Tree of the year: Liquidambar. International Dendrology Society Yearbook 2004: 11-45.
Deterministic Plio-Pleistocene extinctions in the European cool-temperate tree flora. Ecology Letters 6 (7): 646-653. July 2003.
[Possible link between sweetgum fruit and fighting avian flu] Highlights of American Chemical Society meeting in Atlanta, American Chemical Society, March 2006.

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