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The willows are deciduous trees and shrubs in the genus Salix, in the willow family Salicaceae. There are about 350 species in this genus worldwide, found primarily in cooler zones. These plants are dioecious with male and female floweres appearing as catkins on different plants. The deciduous leaves are often elongate and serrate.
The White Willow (Salix alba) is a widespread European species, which has become naturalised on many other parts of the world; it is a tree up to 30 m tall. A variety of it, var. caerulea, selected for fast, straight growth, is grown in southern England, the wood being used for the manufacture of cricket bats.
The Weeping Willow, very widely planted as an ornamental tree, is a cultivar Salix 'Tristis', derived from a hybrid between the Chinese S. babylonica and S. alba.
Some willows, particularly arctic and alpine species, are very small; the Dwarf Willow (Salix herbacea) rarely exceeds 6 cm in height, though spreading widely across the ground.
Almost all willows take root very readily from cuttings or where broken branches lie on the ground.
Medicinal properties
The bark of the willow tree has been mentioned in ancient texts from Assyria, Sumeria and Egypt as a remedy for aches and fever, and the Greek physician Hippocrates wrote about its medicinal properties in the 5th century BC. Native Americans across the American continent relied on it as a staple of their medical treatments.
The active extract of the bark, called salicin, was isolated to its crystaline form in 1828 by Henri Leroux, a French pharmacist, and Raffaele Piria, an Italian chemist, who then succeeded in separating out the acid in its pure state. Salicin is highly acidic when in a saturated solution in water (pH = 2.4), and is called salicylic acid for that reason.
In 1897 Felix Hoffmann created a synthetically altered version of salicin (in his case derived from the Spiraea flower), which caused less digestive upset than pure salicylic acid. The new drug, formally Acetylsalicylic acid, was named aspirin by Hoffman's employer Bayer AG.
| Scientific classification |
| Kingdom: |
Plantae |
| Division: |
Magnoliophyta |
| Class: |
Magnoliopsida |
| Order: |
Malpighiales |
| Family: |
Salicaceae |
| Genus: |
Salix | |
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