Degeneria
| Degeneria | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name of the family | ||||||||||||
| Degeneriaceae | ||||||||||||
| IWBailey & ACSm. | ||||||||||||
| Scientific name of the genus | ||||||||||||
| Degeneria | ||||||||||||
| IWBailey & ACSm. |
Degeneria is a genus of plants within the magnolia-like family that formsits own family Degeneriaceae . It only occurs in Fiji . In contrast to most other members of the flowering plant , they have three to four cotyledons .
description
Appearance and leaf
The two Degeneria species grow as large trees , with Degeneria vitiensis reaching a height of 35 meters and a trunk diameter of one meter. They own essential oils . The leaves are alternate, simple, stalked, and aromatic. They have no stipules . The leaf margin is whole, the blade is pinnately veined. There are no secretion canisters in the blade, but there are round cells with essential oils.
The nodes are pentalacunar, so they have five leaf traces. In the xylem there are fiber tracheids and normal vessels, the ends of which are scalariform (step-shaped). The sieve tube plastids are P-type and have protein crystals and starch .
blossoms
The flowers are hermaphroditic, pollination occurs by insects ( entomophilia ), probably by beetles ( cantharophilia ). The flowers are individually hanging on long pedicels in the axils of leaves. They are medium to large in size. The perianth is divided into a calyx and a crown . The calyx consists of a threefold whorl and is persistent. The 12 to 18 petals are larger than the sepals, fleshy and stand in three to five whorls.
The androeceum consists of 30 to 50 stamens that ripen centripetally. Staminodes occur and stand between fertile stamens and gynoeceum. The stamens are flat and three-veined. The pollen sacs open with longitudinal slits or with elongated flaps. The tapetum of the anther wall is glandular. The monosulcate pollen is distributed individually and is two-celled when released.
The gynoeceum consists of a carpel that is on top. The carpel is incompletely closed, and in anthesis still largely unclosed. A stylus is missing, the scar tissue is along the adjacent amniotic sac margins. The placentation of the ovules is marginal (at the edge) in a row along the lateral margin of the fruit leaf. The ovules have a long funiculus, are anatropic, bitegmic and crassinucellate. The external integument of the ovule does not contribute to the formation of the micropyle. The embryo sac develops according to the polygonum type.
Fruit and seeds
The kidney-shaped and up to 12 centimeters long fruits are leathery with a hard exocarp and contain 20 to 30 seeds with plenty of endosperm , which develops cellularly. This is ruminate and oily. The seed is flat and has an orange-red sarcotesta. The embryo is small but well differentiated and has three (to four) cotyledons . The fruits open, whereupon the seeds hang out of the fruit on the long funiculi. The seeds are spread by birds.
distribution
The genus is endemic to three of the seven "high" islands of the Fiji archipelago, including Viti Levu . There the trees grow on mountain slopes in rainforests .
Systematics
The Degeneriaceae are the sister group of the Himantandraceae within the Magnolia family . The only genus Degeneria I.W.Bailey & ACSm. consists of two types:
- Degeneria vitiensis I. W. Bailey & AC Sm. It occurs in Fiji on the island of Viti Levu .
- Degeneria roseiflora John M. Mill. It occurs in Fiji on the islands of Vanua Levu and Taveuni .
The genus was discovered by Otto Degener in 1941 and named in his honor by IW Bailey and AC Smith in 1942.
Sources and further information
- Degeneriaceae on the AP website (accessed November 11, 2007)
- Degeneriaceae in L. Watson and MJ Dallwitz (1992 onwards), The families of flowering plants (accessed November 11, 2007)
- John M. Miller: Living "Fossil" Magnoliids: Degeneriaceae of Fiji
Individual evidence
- ↑ a b c John M. Miller: Living “Fossil” Magnoliids: Degeneriaceae of Fiji ( Memento of the original from November 6, 2007 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ Keyword Magnoliales in: Encyclopaedia Britannica 2002 DVD Edition . Britannica.com 1994-2002, ISBN 0-85229-797-1 .
- ^ IW Bailey, AC Smith: Degeneriaceae, a new family of flowering plants. Journal of the Arnold Arboretum Volume 23, 1942, pp. 356-365
- ↑ a b Rafaël Govaerts (ed.): Degeneria. In: World Checklist of Selected Plant Families (WCSP) - The Board of Trustees of the Royal Botanic Gardens, Kew . Retrieved April 19, 2020.
- ↑ John M. Miller: A new species of Degeneria (Degeneriaceae) from the Fiji Archipelago . Journal of the Arnold Arboretum, Volume 69, 1988, pp. 275-280. ISSN 0004-2625
- ↑ Archive of the New York Botanical Garden ( Memento of the original from September 30, 2007 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
