Pachypodium ambongense
| Pachypodium ambongense | |
|---|---|
| Scientific classification | |
| Kingdom: | Plantae |
| (unranked): | Angiosperms |
| (unranked): | Eudicots |
| (unranked): | Asterids |
| Order: | Gentianales |
| Family: | Apocynaceae |
| Genus: | Pachypodium |
| Species: | P. ambongense |
| Binomial name | |
|
Pachypodium ambongense Poiss. |
|
Pachypodium ambongense belongs to the dogbane family Apocynaceae, which has recently been merged with the milkweed family Asclepiadaceae. It was first published as a species of the genus Pachypodium in 1924 by the botanist Henri Louis Poisson.
Having a habit as a shrub that is 1 m (3.28 feet) to 2 m (6.56 feet) and bottle-shaped, Pachypodium ambongense inhabits the western low, open deciduous forest of Madagascar on a substrate of Mesozoic calcareous rock. It is fairly rare to the landscape, perhaps, suggesting a more specialized environment needed for it to grow. It is known by common name in Madagascar as "Songosongo" or "Betono."
As a shrub 1 m (3.28 feet) to 2m (6.56 feet) high with a subglobose, not entirely spherical, laterally compressed, flattened on a side habit; it has a diameter ranging from 10 cm ( 3.94 inches) to 40 cm (15.75 inches). Overall it resembles a bottle-shape in habit.
The bark is grey-green and smooth or it has leaf scars. Overall Pachypodium ambongense has a bottle-shaped profile. Its short branches form right below the terminal inflorescence and measure from 7 cm (2.76 inches) to 18 cm (7.09 inches) in diameter. P. ambongense's branchlets are 18 mm (0.71 inch) to 40 mm (1.58 inches) by 5 mm (0.20 inches) to 6 mm (.24 inches). They are covered with paired straight spines, 2 cm (0.79 inch) to 10 cm (3.94 inch) long by 0.5 cm (1.97 inches) to 3 cm (1.18 inches) wide at the base. When young they are sparsely pubescent, or hairy.
The leaves are confined near the apices, the apex or the highest point, of the branchlets. They are petiolate, meaning that they have a leave stalk. The petiole, or stalk roughly, is 2 mm (0.08 inch) to 10 mm (0.39 inch) long. While being sparsely pubescent and hairy, the blade(s) are dark green with a midrib that is pale green above and pale green to pale grey beneath when fresh. When dry, the leave is papery. They are shaped as being (I) ovate--broad and rounded at the base and tapering toward the end—to (II) obovate--egg-shaped and flat, like ovate, but with a narrower end—measuring 1.9 to 3.4 times as long as they are wide. Therefore, the leaves often range in size from 3.5 cm (1.38 inch) to 9 cm (0.35 inch) in length by 1.5 cm (0.59 inch) to 3 cm (1.18 inch) in width. They are obtuse--having a blunt or rounded tip—to rounded in shape at the apex. Cuneate--wedge-shaped, narrowly triangular at the base—or decurrent--having the leaf base that extends down the stem below its point of insertion—into the petiole, the leaves have a margin that is revolute, the margins rolled backwards, and glabrous, smooth above with impressed reticulate venation. They are densely pubescent, hairy, underneath with a midrib and secondary veins prominently showing. There are 23 to 32 secondary veins in pairs, which are straight at the base, up curved at the apex, and forming an angle of 45-85° with the Costa, the rib, ridge in a midrib of a leaf. The tertiary venation is reticulate, either making a net or network of veins or marking with lines resembling a network. They are hidden by the indumentum, any covering of hairs etc., beneath the leaf.
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