Polygala
Polygala vulgaris
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Fabales
Family: Polygalaceae
Tribe: Polygaleae
Genus: Polygala
L.
Type species
Polygala vulgaris
L.
Species

See text

Synonyms
  • Monrosia Grondona 1949
  • Pilostaxis Raf.
  • Triclisperma Nieuwl.

Polygala is a large genus of flowering plants belonging to the family Polygalaceae. They are commonly known as milkworts or snakeroots. The genus is distributed widely throughout much of the world[1] in temperate zones and the tropics.[2] The genus name Polygala comes from the ancient Greek "much milk", as the plant was thought to increase milk yields in cattle.[3]

Description

As traditionally circumscribed, Polygala includes annual and perennial plants, shrubs, vines, and trees.[1] The roots often have a scent reminiscent of wintergreen.[2] The leaf blades are generally undivided and smooth-edged, and are alternately arranged in most species. The inflorescence is a raceme or spikelike array of several flowers; the occasional species bears solitary flowers.[2] The flower is bilateral in shape, with two large petal-like sepals on the sides, often called the "wings",[2] and three smaller sepals behind. There are three petals in shades of reddish purple, yellow or white, which are joined at the bases. The lower of the three is the keel petal, which is "boat-shaped, cucullate [hood-like], or helmet-shaped".[1] The keel petal may have a beak or a fringe on the tip.[2] Stamens and style are within the curve of the keel petal. The fruit is a capsule, sometimes winged. It contains two seeds,[1] which are usually black, hairy and tipped with a large white aril.[2] No members of this genus are known to form nitrogen-fixing nodules.[4]

Taxonomy

The genus Polygala was first described by Carl Linnaeus in 1754. Phylogenetic studies showed that, as traditionally circumscribed, the genus was not monophyletic. It had become a "wastebasket taxon"; almost all species with a flower apparently similar to those of the Papilionoideae – two petaloid lateral sepals forming 'wings', two petals forming a 'standard', and one petal forming a 'keel', plus a bilocular fruit capsule – were placed in Polygala, while species with more obviously specialized features, particularly those of the fruit, were placed in other genera. In 2011, John Richard Abbott separated some more sharply defined genera from Polygala.[5]

Species

Partly because of differing circumscriptions, the reported number of valid species in the genus varies from about 350[6][7] to 500[1][2] to 725[8] or 730.[9] The Americas have the most species, especially South America,[9] with Africa second in diversity and Asia third.[8] As of April 2020, Plants of the World Online accepted about 660 species in the genus Polygala. These include:[10]

Polygala amara
Polygala lutea
Polygala myrtifolia
Polygala nana
Polygala poaya

Species now placed in other genera:

Hybrid

Polygala × dalmaisiana (of garden origin)

Ecology

Polygala species are used as food plants by the larvae of some Lepidoptera species including large grizzled skipper.

Cultivation

Some species are valued in cultivation. Polygala × dalmaisiana, an evergreen shrub, has gained the Royal Horticultural Society's Award of Garden Merit.[12]

References

Wikimedia Commons has media related to Polygala.
  1. 1 2 3 4 5 Polygala. Flora of China.
  2. 1 2 3 4 5 6 7 Polygala. The Jepson eFlora 2013.
  3. ↑ Coombes, A. J. (2012). The A to Z of Plant Names. USA: Timber Press. pp. 312. ISBN 9781604691962.
  4. ↑ Dilworth, M. J. (2008). Nitrogen-fixing leguminous symbioses (in Spanish). Dordrecht: Springer. ISBN 978-1-4020-3548-7. OCLC 226076050.
  5. ↑ Abbott, J. Richard (2011). "Notes on the disintegration of Polygala (Polygalaceae), with four new genera for the Flora of North America". Journal of the Botanical Research Institute of Texas. 5 (1): 125–137. JSTOR 41972495.
  6. ↑ Coelho, V. P. D. M., et al. (2008). Flora of Paraíba, Brazil: Polygala L.(Polygalaceae). Acta Botânica Brasilica 22(1), 225-39. (Portuguese)
  7. ↑ Coelho, V. P. D. M., et al. (2008). Flora of Paraíba, Brazil: Polygala L.(Polygalaceae). Acta Botânica Brasilica 22(1), 225-39. (Portuguese)
  8. 1 2 Lüdtke, R., et al. (2013). The genus Polygala L.(Polygalaceae) in Southern Brazil. Hoehnea 40(1), 1-50. (Portuguese)
  9. 1 2 Pastore, J. F. B. and T. B. Cavalcanti. (2008). A New Species of Polygala (Polygalaceae) from Brazil. Novon 18(1), 90-93.
  10. ↑ "Polygala Tourn. ex L.", Plants of the World Online, Royal Botanic Gardens, Kew, retrieved 2020-04-13
  11. ↑ Dickinson, T., et al. (2004). ROM Field Guide to Wildflowers of Ontario. Royal Ontario Museum, Toronto. McClelland and Stewart Ltd. p 336.
  12. ↑ "RHS Plant Selector - Polygala × dalmaisiana". Retrieved 13 April 2020.
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