Oncocalamus

Oncocalamus is a native of tropical Africa, climbing palm species. In the family unique are the flower clusters.

• 4.1 Notes and references

Features

The representatives are multi-stemmed, climbing Rattanpalmen with pinnate leaves. They are armed with spines, several times flourishing and monoecious getrenntgeschlechtig ( monoecious ). The stem is circular in cross section and has long internodes.

The chromosome number is unknown.

The leaves are pinnate, with young plants in two parts ( bifid ) and carrying a terminal Cirrus. The leaf sheath is Roehrig and bears scattered black, triangular rigid spines and a scattered pubescence. The petiole is usually very short and lacking in mature, flowering stems. The rachis is covered with spines, equal to the vagina. The Cirrus is wearing a pair of bent-back Akanthophylle. The leaf blade is composed of a few to numerous leaflets together, most of which are simply folded, entire, acuminate, lanceolate to slightly sigmoidal. They are busy on thickened leaf margin with fixed spines. The proximal leaflets are often smaller than the other and strongly reinforced and bent back over the trunk away.

Inflorescences

The inflorescences are once branched. The peduncle is enclosed in the leaf sheath. The cover page is Roehrig, close-fitting, zweikielig and bilobed at the tip. It is shorter than the sheath of the liner sheet. On Peduncle there are usually four distich standing bracts, the first fit snugly scheidig, later tearing along. The inflorescence axis is longer than the peduncle, its bracts are similar to those of the stem. The first-order lateral axes are hanging or protruding and have a basal, zweikieliges, röhriges cover sheet and numerous distich standing, short -tubed, slightly inflated bracts. Each of these encloses a flower clusters. After flowering, they can tear irregularly. The flower clusters is partially obscured by a tubed, zweikieligen cover sheet and consists of up to eleven flowers which. Selected from a group with one or three central female flower and two lateral wrapping of two to four male flowers consist Each flower except the central female has an open, spatulate, zweikielige, vorblattähnliche Brakteole. The exact morphology of flower clusters is not understood.

Flowers

The male flowers are symmetrical. The calyx is membranous, stalked, Roehrig and ends in three short triangular, pointed lobes. The crown standing above the cup only slightly and is almost reached to the base in three divided valvate lobes. The six stamens are fused with their stamens to a thick, fleshy tube. At the top are six shallow lobes on the inside are hanging, round, latrorse anthers. The stamp rudiment is very narrow, conical and projecting slightly above the stamen tube out. The pollen is ellipsoidal and bisymmetrical. The germ is opening a distal sulcus. The longest axis measures 29-29 microns.

The female flowers superficially resemble the male, are somewhat wider. Calyx and corolla are similar. At the staminodes tube are small, empty anthers. The gynoecium consists of three carpels, contains three ovules. It is ellipsoidal and occupied me shed. The style is long, narrow and triangular.

Fruit and seeds

The fruit is rather spherical and bears apical small scar remains. The exocarp is busy with vertical rows of thin scales. The mesocarp is very thin and lacks the fruit ripening almost completely. The endocarp is not differentiated. Each fruit contains just one seed, which attaches basally with an oval hilum. He has a sarcotesta. The endosperm is homogeneous and laterally pressed hard by a mass of the inner seed coat.

Dissemination and locations

The species are found in equatorial West Africa and the Congo Basin. They are restricted to tropical lowland rainforests.

System

The genus Oncocalamus is placed in the subfamily Calamoideae, Tribe Lepidocaryeae, subtribe Ancistrophyllinae within the family Arecaceae. The monophyly of the genus has not yet been studied ( as of 2008).

In the World Checklist of Selected Plant Families of the Royal Botanic Gardens, Kew, the following types are recognized:

• Oncocalamus djodu
• Oncocalamus macrospathus
• Oncocalamus mannii
• Oncocalamus tuleyi
• Oncocalamus wrightianus

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.