Rhopaloblaste

Rhopaloblaste is a genus of palm trees. They grow in tropical lowland rain forests as undergrowth or in the middle layer, rare in the upper tree layer.

Features

The representatives of the genus are medium-sized, single -stemmed palm trees 15-20 m tall. Only Rhopaloplaste is slim singaporensis, more stocky and less than 5 m tall. The base of the stem is often thickened. All representatives are unarmed and monoecious. The stem is slender depending on the type (2 to 4 cm in diameter) or thick (up to 35, rarely 40 cm) The leaf scars are clearly visible and eye-catching rings. The outer part of the trunk is black and very hard, the inner soft with few fibers.

The crown consists of 5 to 17 leaves. The long -tubular leaf sheaths form a distinct Kronschaft at the root end. The rachis and base of the leaflets are occupied at the tops with brown-black, membranous scales. The top of the leaflets are dark green and glossy, the lower dull green or pale. Already the first leaf of the seedling ( Eophyll ) is finely pinnately divided.

Leaf sheath, leaves and inflorescence are distinctly hairy, and there are different types of hair. Sealing standing, brown to gray-brown, overlapping scales can be found on the leaf sheaths; pressed- membranous scales on the petiole; twisted, brown - black membranous scales on the rachis, which are densely especially at the base of the pinnae; and reddish-brown to gray-brown scales along the underside of the midrib of the leaflets. In the inflorescence, the coat is thinner, to the young side arms are irregular scales and sometimes star hair.

The inflorescence is between the sheets and is mono-to tetrasubstituted branched, rarely five times. The two lower branches are strongly recurved, with the exception of singaporensis Rhopaloblaste. Here, the inflorescence is reduced. In the bud stage, the inflorescence axes as viscera cover sheet and liner sheet are rolled. The peduncle is short, the inflorescence axis between 35 and 100 cm long. It bears numerous lateral axes.

The flowers are along the side axes in triads with a central female and two lateral male flowers. The male are slightly longer than the female. Each triad stands in the axils of a lip-shaped bract, only at Rhopaloblaste ceramica they are in small pits. Male and female flowers have three short, strongly overlapping, rounded sepals. The petals of the female flowers are similar to the sepals, the male are longer and are klappig. The male blossoms have six stamens, which are bent inwards in the bud. Their stamens are fused at the base, the ovary - rudiment is cone-shaped, almost as long as the stamens. In the female flower are four staminodes that have grown irregularly lobed ring. The ovary is irregularly ovoid, has a seed tray ( is unilocular ), a stylus missing, but there are three conspicuous, apical standing scars.

Shape and size of the fruits are important features to distinguish the species. They are usually symmetrical, ceramica only Rhopaloblaste slightly asymmetrical. The shape ranges from oval to round over ellipsoidal. They are 10 to 35 mm long and 8-16 mm wide. Immature they are green, to maturity, they are orange - yellow to red. The scars remain apically to the fruit, the perianth also remains on the fruit, in different sizes. The exocarp is smooth, the mesocarp contains no fiber - sclereids or tannin cells, it flat longitudinal fibers in one or more of several layers at the edge of the yellow endocarp.

The shape of the seed is similar to the fruit. The seeds are brown to black, the hilum is mild to severely depressed on the adaxial side. The endosperm is deeply furrowed, the embryo is basal and club-shaped.

Distribution and ecology

The genus is found in Southeast Asia and has a very disjoint area. In the western region, a species occurs on the Nicobar Islands, another on the Malay Peninsula and Singapore. To the east it is missing in Sumatra, Java, Borneo, Sulawesi, the Lesser Sunda Islands and the Philippines. In the Moluccas and New Guinea, two species occur, and there are no occurrences in the eastern part of New Guinea. Depending on a species occurs on New Ireland and the Solomon Islands.

The representatives grow in the tropical rain forest to 900 m above sea level. They usually grow in lowland rain forests and in low-lying mountain forests, in middle and high mountain areas they are missing. They establish themselves easily in secondary forests and abandoned gardens.

System

The genus Rhopaloblaste is placed in the subfamily Arecoideae, Tribe Areceae within the palm family, but not assigned to subtribe here.

Banka and Baker accepted in its generic revision 2004 six types:

• Rhopaloblaste augusta on the Nicobar Islands
• Rhopaloblaste ceramica from the Moluccas to New Guinea
• Rhopaloblaste elegans in the Solomon Islands
• Rhopaloblaste gideonii on New Ireland
• Rhopaloblaste ledermanniana in New Guinea
• Rhopaloblaste singaporensis on the Malay Peninsula and Singapore

Documents

• Roy Banka, William J. Baker: A monograph of the genus Rhopaloblaste ( Arecaceae ). Kew Bulletin, Volume 59, 2004, pp. 47-60.