Acaciella angustissima
fern acacia, prairie acacia, whiteball acacia
10–210 mm;
stipules linear, to 6.5 mm, margins ciliate;
petiole 3.5–65 mm, glabrous or appressed-pubescent to pilose;
pinnae 2–17[–32] pairs, 6–50[–105] mm;
rachis 5–200 mm;
leaflets 7–85 pairs per pinna, blades linear, 2–3.5[–4] × 0.5–1.3 mm, base oblique and obtuse, only midvein prominent abaxially, apex broadly acute to obtuse.
usually solitary, rarely 2 or 3, axillary or terminal, pseudoracemes or pseudopanicles, to 280 mm, 9–18 mm diam.;
pedicels present.
5–21 mm.
calyx 0.6–1.2 mm;
corolla 1.9–4.5 mm;
filaments 3–7.6 mm.
25–90 × 5.5–17 mm, rarely constricted between seeds.
Acaciella angustissima
Varieties 3 (2 in the flora).
Acaciella angustissima is the most widespread and morphologically variable species of Acaciella. Segregate species, subspecies, varieties, and forms have been recognized based on habit, leaflet shape, stem and leaflet indument, stem striations, number of pinnae, and leaflets per pinna. Acaciella angustissima is common in disturbed habitats, particularly roadsides and pastures, and it is becoming common throughout much of the tropical and subtropical regions where it was introduced originally as a forage crop. With a geographic range that extends from the southern and central United States to northern Argentina, A. angustissima is highly variable in many characteristics, one of the most obvious being plant size, which ranges from subshrubs that are sometimes nearly herbaceous, to trees exceeding ten meters. M. L. Rico-Arce and S. Bachman (2006) recognized three varieties and indicated that all three occur in North America north of Mexico. The two varieties described here are common in the central and southwestern United States. No specimens of the third variety [var. filicioides (Cavanilles) L. Rico] in the flora area have been located.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Leaflets (20–)23–40 pairs per pinna; pinna 9–17 pairs; stems white-puberulent or yellow-hirsute. | var. angustissima |
1. Leaflets 7–20(–22) pairs per pinna; pinnae 2–6(or 9) pairs; stems glabrous. | var. texensis |
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