Thrinax

Thrinax radiata

Thrinax is a native to the Caribbean islands and the adjacent mainland palm genus.

• 5.1 Notes and references

Features

The representatives are small to medium-sized, single -born non-reinforced palms. They are several times flourishing and hermaphrodite. The stem is erect, columnar, smooth or fibrous and provided with annular leaf scars. Usually are numerous fibrous roots at the stem base.

The chromosome number is 2n = 36

The leaves are induplicat, fan-shaped and often irregularly divided. The leaf sheath tears open at both ends: opposite the petiole and abaxial. She dissolves into irregular fibers. The vagina is densely covered with a later falling hair. The petiole is long and slender. He is roundish to slightly furrowed on both sides, the side edges are rather sharp. The Hastula on the adaxial side ( upper leaf surface ) is striking, long- pointed, often curled, the abaxial Hastula is smaller, round or triangular and may be absent. The leaf blade is fan-shaped, which are often irregularly shaped individual segments are connected to each other in the lower half. They are lanceolate, acuminate, usually with a two-part tip. The upper leaf surface is glabrous, the lower surface often covered with scales, sometimes white. The midrib and also the marginal ribs are striking.

Inflorescences

The inflorescences are between the sheets ( intrafoliär ). They are slender, upright branches arching up and duplicate. The first-order lateral axes are continuous. The peduncle is more slender and circular in cross section. The cover sheet is short, Roehrig, zweikielig, hairy and opens distally. There are several bracts on the inflorescence stalk, similar to the previous sheet, but are not keeled. They overlap and envelop scheidig the stem. The inflorescence axis is longer than the stem and slender. At her are spirally arranged long -tube bracts, the lateral branches of the first order sit in their armpits. These have a short free portion on which a zweikieliges, two-piece cover sheet sits. At spiral standing, narrow, triangular bracts the flower-bearing side branches arise ( Rachillae ). These are slender, rather short and stiff. On them are spirally small triangular bracts which bear the solitary flowers. Brakteolen likely to be missing.

Flowers

The flowers are at eye-catching stems. The perianth forms a single cup with six lobes or teeth. Most are 6-12 stamens present. Their stamens are very slender, sometimes interconnected basal. The anthers are oblong, stamens set dorsifix to the lower area of ​​the outside of the anther. The anthers are latrors. The gynoecium consists of a single carpel, which is unilocular and contains only one ovule. This sits basal, erect and campylotrop, but slightly askew, so that the micropyle to the upper dorsal wall of the seed compartment has. Basal ovule is surrounded by an aril.

The pollen is ellipsoidal with mild to significant asymmetry. The germ is opening a distal sulcus, a rare dreistrahliger sulcus. The longest axis measures 24-46 microns.

Fruit and seeds

The fruit is very small and white to maturity. The scar remains are at the top, often remnants of the perianth are available. The exocarp of fresh fruit is smooth, the mesocarp is thin and mealy, the endocarp is very thin and papers. The seed is compressed - globose, smooth, smooth scar has ( hilum ). The branches of the raphe are pressed hard and cause a segmentation of the endosperm, which is otherwise homogeneous.

Dissemination and locations

Two species are endemic to Jamaica. The third type is widespread in coastal regions of Honduras, Belize, Mexico and the northern Caribbean. On Jamaikca the three types are separated by location: Thrinax parviflora grows in dry evergreen forests and thickets, Thrinax excelsa grows in lowland rainforest and Thrinax radiata in coastal salt- affected forests and thickets.

System

The genus Thrinax is placed in the subfamily Coryphoideae, Tribe Cryosophileae within the family Arecaceae. The genus is monophyletic. You may be the sister group to the group from Schippia and Cryosophila.

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

• Thrinax excelsa, endemic to Jamaica
• Thrinax parviflora, endemic to Jamaica
• Thrinax radiata

Fossil history

Among the fossils, which were compared with extant species of Thrinax, Thrinax include leaves of eocenica from the Middle Eocene of southeastern North America ( Claiborne flora) and Palaeothrinax mantelli from the lower to middle Oligocene of the Isle of Wight. A Thrinax Tranquillus designated as pollen is on its form, however, in the subfamily Coryphoideae very often.

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. 232-234.