Oncocalamus
| Oncocalamus | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Oncocalamus | ||||||||||||
| ( G. Mann & H. Wendl. ) H. Wendl. |
Oncocalamus is a climbing palm genus native to tropical Africa. The flower clusters are unique in the family.
features
The representatives are multi-stemmed, climbing rattan palms with pinnate leaves. They are armed with spines, bloom several times and are single sexed ( monocyte ). The trunk is circular in cross section and has long internodes .
The number of chromosomes is unknown.
leaves
The leaves are pinnate, bifid in young plants and have a terminal cirrus. The leaf sheath is tubular and has scattered black, triangular rigid spines and scattered hairs. The petiole is usually very short and absent from fully grown, flowering stems. The rachis is studded with spines, like the scabbard. The cirrus carries a pair of recurved acanthophylls . The blade is composed of a few to numerous leaflets, which are usually simply folded, entire, pointed, lanceolate to slightly sigmoidal. They are covered with firm spines on the thickened leaf margin. The proximal leaflets are often smaller than the rest and are heavily reinforced and bent back over the trunk.
Inflorescences
The inflorescences are branched once. The peduncle is enclosed in the leaf sheath. The cover sheet is tubular, close-fitting, two-keeled and bilobed at the tip. It is shorter than the leaf sheath of the bract. On the peduncle there are usually four distich bracts , which are initially tightly spaced and later tear open lengthways. The inflorescence axis is longer than the stalk, its bracts resemble those of the stalk. The lateral axes of the first order are hanging or protruding and have a basal, two-keeled, tubular cover leaf and numerous distich, short, tubular, somewhat inflated bracts. Each of these encloses a ball of flowers. After flowering, they can tear irregularly. The flower ball is partially covered by a tubular, two-keeled cover sheet and consists of up to eleven individual flowers, which consist of a group with one or three central female flowers and two lateral coils of two to four male flowers. Each flower except the central female has an open, spatulate, two-keeled, bracteole-like bracteole . The exact morphology of the flower clusters has not been researched.
blossoms
The male flowers are symmetrical. The calyx is membranous, stalked, tubular and ends in three short triangular, pointed lobes. The crown protrudes only a little beyond the calyx and is divided into three long, valvate lobes almost to the base . The six stamens are fused with their stamens to form a thick, fleshy tube. At the top are six shallow lobes, on the inside of which there are hanging, round, latrorse anthers . The rudiment of the pistil is very narrow, conical and protrudes slightly beyond the stamen. The pollen is ellipsoidal and bisymmetrical. The germ opening is a distal sulcus. The longest axis measures 29 to 29 microns.
The female flowers are superficially similar to the male ones, but are somewhat wider. The calyx and crown are similar. There are small, empty anthers on the staminodes . The Gynoeceum consists of three fused carpels , contains three ovules . It is ellipsoidal and filled with scales. The stylus is long, narrow and triangular.
Fruits and seeds
The fruit is more spherical and has small remnants of scars apically . The exocarp is covered with vertical rows of thin scales. The mesocarp is very thin and is almost completely absent when the fruit is ripe. The endocarp is not differentiated. Each fruit contains only one seed that starts at the base with an oval hilum. He has a sarcotesta . The endosperm is homogeneous and deeply indented laterally by a mass of the inner seed coat.
Distribution and locations
The species occur in equatorial West Africa and in the Congo Basin . They are limited to tropical lowland rainforests.
Systematics
The genus Oncocalamus (G.Mann & H.Wendl.) H.Wendl. is placed within the family Arecaceae in the subfamily Calamoideae , Tribe Lepidocaryeae , Subtribus Ancistrophyllinae. The monophyly of the genus has not yet been investigated (as of 2008).
The Royal Botanic Gardens, Kew's World Checklist of Selected Plant Families recognizes the following species:
- Oncocalamus djodu De Wild. : The home is Zaire .
- Oncocalamus macrospathus Burret : The home is tropical western and tropical central Africa.
- Oncocalamus mannii (H. Wendl.) H. Wendl. : The home is the southern Cameroon to Gabon.
- Oncocalamus tuleyi Sunderl. : The homeland stretches from southeastern Nigeria to western Cameroon.
- Oncocalamus wrightianus Hutch. : The homeland ranges from southern Benin to southwestern Nigeria.
supporting documents
- John Dransfield, Natalie W. Uhl, Conny B. Asmussen, William J. Baker, Madeline M. Harley, Carl E. Lewis: Genera Palmarum. The Evolution and Classification of Palms . Second edition, Royal Botanic Gardens, Kew 2008, ISBN 978-1-84246-182-2 , pp. 147-148.
Individual evidence
- ↑ Rafaël Govaerts (ed.): Oncocalamus. In: World Checklist of Selected Plant Families (WCSP) - The Board of Trustees of the Royal Botanic Gardens, Kew . Retrieved November 6, 2014.
Web links
- Oncocalamus on the homepage of the Fairchild Tropical Botanic Garden