Oncotheca
| Oncotheca | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name of the family | ||||||||||||
| Oncothecaceae | ||||||||||||
| Kobuski ex Airy Shaw | ||||||||||||
| Scientific name of the genus | ||||||||||||
| Oncotheca | ||||||||||||
| Baill. |
Oncotheca is the only genus of plants of the family Oncothecaceae in the order Icacinales within the class of flowering plants (Magnoliopsida). The only two species are only found in New Caledonia .
description
The Oncotheca species grow as evergreen shrubs or trees . The wood anatomy is relatively unspecialized: the vessels stand individually and have a small diameter, they are network trachea. The nodes are multilacunar.
The alternate and spirally arranged leaves are concentrated at the branch ends and have at least a short stalk. The leathery leaf blade is simple , obscure-lanceolate and pinnate. The cuticle and hypodermis are thick, the mesophyll is thick and spongy. These characteristics are interpreted as an adaptation to the extremely nutrient-poor locations ( peinomorphosis ). The leaf margin is smooth or serrated. There are no stipules.
The lateral, thyrsoid branched total inflorescences are composed of zymous partial inflorescences. There are bracts . The relatively small, hermaphrodite flowers are radial symmetry and five-fold with a double flower envelope . There are five sepals . The five petals are bell-shaped briefly fused. There is only one circle (the outer circle is missing - the stamens alternate with the petals) with five fertile stamens that are free from one another. The stamens are short. Five carpels have become a top permanent ovary grown, with two suspended ovules per subject. There are five free, short styluses .
The fruits are two- to five-seeded, fleshy closing fruits similar to the stone fruit . The two (rarely three) cotyledons ( cotyledons ) are short.
The two species differ mainly in fruit shape, leaf size and stamen morphology .
Systematics and distribution
The genus Oncotheca was established in 1891 by Henri Ernest Baillon in Bulletin Mensuel de la Société Linnéenne de Paris , 2, p. 931. Type species is Oncotheca balansae Baill. The generic name Oncotheca is derived from the Greek words oncos for mass and theke for box. The Oncothecaceae family was established in 1965 by Clarence Emmeren Kobuski in Airy Shaw : Kew Bulletin , Volume 18, Issue 2, p. 264.
The genus Oncotheca was previously assigned to the families Aquifoliaceae or Ebenaceae , and in 1965 described as a separate family Oncothecaceae. Arthur John Cronquist and Armen Tachtajyan placed them in the order of Theales. Molecular genetic studies did not result in a systematic assignment to an order until 2015. The Oncothecaceae are allocated within the Euasteriden I according to APG IV of the order Icacinales established in 2015 . Most closely related are the Metteniusaceae .
The genus Oncotheca was monotypical until a second species was described in 1982. There are only two species in this genus and family. Both species are only found in New Caledonia and thrive along rivers or in other slightly humid locations, mainly on the southernmost tip of the Southern Province:
- Oncotheca balansae Baill. : The chromosome number is 2n = 50.
- Oncotheca humboldtiana (Guill.) Morat & Veillon (Syn .: Oncotheca macrocarpa Guill. )
swell
- The Oncothecaceae family on the AP website . (Sections systematics and description)
- The Oncothecaceae family at DELTA by L. Watson & MJ Dallwitz. (Section description)
- Keith M. Cameron: On the phylogenetic position of the New Caledonian endemic families Paracryphiaceae, Oncothecaceae, and Strasburgeriaceae: A comparison of molecules and morphology. In: The Botanical Review. Volume 68, No. 4, 2002, ISSN 0006-8101 , pp. 428-443, doi : 10.1663 / 0006-8101 (2002) 068 [0428: OTPPOT] 2.0.CO; 2 .
- Kenneth M. Cameron: On the phylogenetic position of the New Caledonian endemic families Paracryphiaceae, Oncothecaceae, and Strasburgeriaceae: a comparison of molecules and morphology. In: The Botanical Review , 2002. Full text online.
Individual evidence
- ↑ a b Oncothecaceae at Tropicos.org. Missouri Botanical Garden, St. Louis
- ↑ Umberto Quattrocchi: CRC World Dictionary of Plant Names: Common Names, Scientific Names, Eponyms, Synonyms, and Etymology . tape 3 . CRC Press, 1999, ISBN 978-0-8493-2673-8 , pp. 1876 ( Oncotheca in the Google book search).
- ↑ The Angiosperm Phylogeny Group: An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG IV . Botanical Journal of the Linnean Society, 2016, Volume 181, pp. 1-20. doi : 10.1111 / boj.12385
- ^ Favio González, Julio Betancur, Olivier Maurin, John V. Freudenstein, Mark W. Chase: Metteniusaceae, an early-diverging family in the lamiid clade. In: Taxon. Volume 56, No. 3, 2007, ISSN 0040-0262 , pp. 795-800.
- ↑ a b Kenneth M. Cameron: On the phylogenetic position of the New Caledonian endemic families Paracryphiaceae, Oncothecaceae, and Strasburgeriaceae: a comparison of molecules and morphology. In: The Botanical Review , 2002. Full text online.
- ^ Oncotheca balansae at Tropicos.org. In: IPCN Chromosome Reports . Missouri Botanical Garden, St. Louis
Web links
- Oncotheca balansae , Oncotheca humboldtiana Photos and distribution maps of the two species on www.endemia.nc .