Acaciella angustissima

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

Nomeclature

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.

Varieties

● 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

Synonyms

● 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.

History

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.

Description

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.