Persea
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| Missing image Persea_borbonia.jpg Persea borbonia foliage and fruit | ||||||||||||
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Many, including: |
Persea is a genus of about 150 species of evergreen trees belonging to the laurel family, Lauraceae. The best-known member of the genus is the Avocado P. americana, widely cultivated in subtropical regions for its large, edible fruit.
They are medium-size trees, 15-30 m tall at maturity. The leaves are simple, lanceolate to broad lanceolate, varying with species from 5-30 cm long and 2-12 cm broad, and arranged spirally or alternately on the stems. The flowers are in short panicles, with six small greenish-yellow perianth segments 3-6 mm long, nine stamens and an ovary with a single embryo. The fruit is an oval or pear-shaped drupe, with a fleshy outer covering surrounding the single seed; size is very variable between the species, from 1-1.5 cm in e.g. P. borbonia and P. indica, up to 10-20 cm in P. americana.
The species of Persea have a disjunct distribution, with about 70 Neotropic species, ranging from Brazil and Chile in South America to Central America and Mexico, the West Indies, and the southeastern United States; a single species, P. indica, endemic to the Macaronesian islands, including Madeira and the Canary Islands; and 80 species inhabiting east and southeast Asia. None of the species is very tolerant of severe winter cold, with the hardiest, P. borbonia, P. ichangensis and P. lingue, surviving temperatures down to about -12°C; they also require continuously moist soil, and do not tolerate drought.
Fossil evidence indicates that the genus originated in West Africa during the Paleocene, and spread to Asia, to South America, and to Europe and thence to North America. It is thought that the gradual drying of Africa, west Asia, and the Mediterranean from the Oligocene to the Pleistocene, and the glaciation of Europe during the Pleistocene, caused the extinction of the genus across these regions, resulting in the present distribution.
Classification
The genus Persea is treated in three subgenera. The Asian subgenus Machilus is treated in a separate genus Machilus by many authors, including in the Flora of China, while graft-incompatibility between subgenus Persea and subgenus Eriodaphne suggests that these too may be better treated as distinct genera. Another closely related genus Beilschmiedia is also sometimes included in Persea.
- Subgenus Persea - Central America
- P. americana
- P. americana var. drymifolia
- P. americana var. floccosa
- P. americana var. guatemalensis
- P. americana var. nubigena
- P. americana var. steyermarkii
- P. schiedeana
- P. americana
- Subgenus Eriodaphne - The Americas, Macaronesia
- P. alpigena
- P. borbonia
- P. caerulea
- P. cinerascens
- P. donnell-smithii
- P. indica (possibly better treated in a fourth subgenus of its own)
- P. lingue
- P. longipes
- P. palustris
- P. skutchii
- Subgenus Machilus - Asia
- P. edulis
- P. ichangensis
- P. japonica
- P. macrantha
- P. nanmu
- P. thunbergii
- P. yunnanensis
External links
- Avocado source Extensive information on the Avocado and the genus generally, particularly the subgenera Persea and Eriodaphne
- Flora of China Full list of species in Machilus in China