Tuesday, 27 August 2019

Alstonia in Malesia

Alstonia is a widespread genus of evergreen trees and shrubs, of the dogbane plant family Apocynaceae.  It consists of about 40-60 species, native to tropical and subtropical Africa, Central America, southeast Asia, Polynesia and Australia.


Alstonia was named by Robert Brown in 1811, after Charles Alston (1685–1760), a professor of botany at Edinburgh from 1716-1760.


The leathery, sessile, simple leaves are elliptical, ovate, linear or lanceolate and wedge-shaped at the base. The leaf blade is dorsiventral, medium-sized to large and disposed oppositely or in a whorl and with entire margin. The leaf venation is pinnate, with numerous veins ending in a marginal vein.  Phyllotaxy is whorled i.e. two or more leaves arises at a node and form a whorl.

The inflorescence is terminal or axillary, consisting of thyrsiform cymes or compound umbels. The small, more or less fragrant flowers are white, yellow, pink or green and funnel-shaped, growing on a pedicel and subtended by bracts. They consist of 5 petals and 5 sepals, arranged in four whorls. The fertile flowers are hermaphrodite.


Alstonia has 5 distinct sections, each a monophyletic group; Alstonia ( including Winchia ), Blaberopus, Tonduzia. Monuraspermum, and Dissuraspermum.

Species of the section Memuraspermum have no latex in the trunk bark, in contrast to the species of section Alstonia, where latex may be observed in all parts of the plant.

The leaves of Alstonia are opposite or whorled.  Opposite leaves are found in most species of Dissuraspermum.  Worled leaves are found in the other sections.



Alstonia species native to Malay Archipelago :
A. angustifolia A.DC. - Borneo, Malaya, Sumatra
A. angustiloba Miq. - Borneo, Malaya, Sumatra, Thailand, Java
A. curtisii King & Gamble - Thailand
A. glancescens Guillaumin - New Caledonia
A. macrophylla Wall. ex G.Don –  S China, Sri Lanka, SE Asia, New Guinea
A. neriifolia D.Don - Nepal, Sikkim, Bhutan
A. parvifolia Merr. - Philippines
A. penangiana K.Sidiyasa - Penang Hill
A. pneumatophore Backer ex L.G.Den Berger - Malaya, Borneo, Sulawesi, Sumatra
A. rupestris Kerr - Thailand
A. scbolaris (L.) R.Br.  - E+S+SE Asia, Papuasia, N Australia
A. spatulata Blume - SE Asia, New Guinea
A. spectabilis R.Br.  - SE Asia, Papuasia, N Australia

Alstonia trees are widespread and mostly not endangered.

Endangered : A. annamensis
Vulnerable : A. penangiana, A. beatricis, A, breviloba, Al rubiginosa …
Least Concern : A. angustifolia, A. macrophylla, A. pneumatophore, A. rupestris, A. scholaris, A. spatulata, A. spectabilis …

1. Wikipedia
2. Kade Sidiyasa, 1998, Taxonomy, Phylogeny, and Wood Anatomy of Alstonia
3. Joseph Monachino, 1949, A Revision of the Genus Alstonia, PACIFIC SCIENCE, Vol. III. April 1949
4. IUCN Red List

Wednesday, 21 August 2019

Acaciella angustissima

Acaciella angustissima ( white ball acacia) is a highly variable perennial shrub native to subtropical and tropical America.


The name Acaciella is diminutive of the genus Acacia

Angustissima is the ablative feminine singular of angustissimus, which means narrowest or very narrow, depicting its narrow leaflets.


Acaciella angustissima var. angustissima (Mill.) Britton & Rose
Acaciella angustissima var. chisosiana Isely
Acaciella angustissima var. filicioides (Cav.) L. Rico
Acaciella angustissima var. hirta (Torrey & A.Gray) Robinson
Acaciella angustissima var. shrevei (Britton & Rose) Isely
Acaciella angustissima var. suffrutescens (Rose) Isely
Acaciella angustissima var. texensis (Torrey & A.Gray) Isely


Acacia angulosa Bertol.
Acacia angustissima (Mill.) Kuntze
Acacia elegans M.Martens & Galeotti[2]
Acacia filicina Willd.
Acacia filicioides (Cav.) Trel.
Acacia glabrata Schltdl.
Acacia hirsuta Schltdl.
Acacia insignis M. Martens & Galeotti
Acacia pittieriana Standl.
Acacia villosa (Sw.) Willd.

Acaciella angulosa (Bertol.) Britton & Rose
Acaciella costaricensis Britton & Rose
Acaciella holtonii Britton & Killip
Acaciella martensis Britton & Killip
Acaciella rensonii Britton & Rose
Acaciella santanderensis Britton & Killip
Acaciella villosa (Sw.) Britton & Rose

Mimosa angustissima Mill.
Mimosa filicioides Cav.
Mimosa ptericina Poir.


1768 - first described as Mimosa angustissima.
1896 - transferred to the genus Acacia by Kuntze.
1928 - Britton and Rose proposed a new genus Acaciella
2006 - Rico Arce and Bachman confirmed the genus Acaciella.  
15 species described in America.


Acaciella angustissima is morphologically highly variable.

The following description is of the typical form of the species ( A. angustissima var. angustissima), which was described by  Rico Arce and Bachman in 2006 :

A thornless shrub or small tree usually growing 2–7 m tall with a single short trunk. However, it may very rarely reach up to 12 m in height.

Its younger stems are hairless or finely hairy and are usually somewhat striate

The leaves are bipinnate, 10–21 cm long, and usually have 10–17 pairs of pinnae.  They are borne on stalks 1.2–3.5 cm long that are sparsely strigulose. The pinnae are 2.5–5 cm long and each bears 20–40 pairs of leaflets. These relatively narrow leaflets are small (2.4–5 mm long and 0.5–2 mm wide) with pointed tips and entire margins.

Stipules are inconspicuous (2–2.5 mm long).

The whitish flower clusters are globular or ellipsoidal in shape (1–1.5 cm across) and are actually short head-like racemes. They are borne on short peduncles (1–1.5 cm long) and arranged in axillary fascicles, which may sometimes be arranged into larger panicle-like inflorescences.

The flat, thin-walled, papery, pods are oblong in shape (3–9 cm long and 6–15 mm wide) with straight or sinuate margins. They are initially green (Figure 5), but turn coffee-brown when ripe. These glabrous pods are acute at the base and apex, with a stipe 7–12 mm long and a beak 2–7 mm long.

Each pod contains 8–12 circular seeds 2.5–3.2 mm across. These seeds are arranged transversely in the pod and are clearly separated from each other. Seed production is prolific. Seed weight is 90 000–100 000 seeds/kg.