Acaciella
N. Amer. Fl. 23: 96. 1928.
Trees, shrubs, [herbs or subshrubs], unarmed. Stems erect [to spreading], glabrous or pubescent; twigs terete to angulate, straight, short-shoots absent. Leaves alternate, even-bipinnate; stipules present, caducous or persistent, herbaceous; petiolate, petiole channeled; pinnae 1–32 pairs, mostly opposite; leaflets 2–numerous pairs per pinna, opposite, sessile or subsessile, blade margins entire, surfaces glabrous [pubescent]. Inflorescences [4–]10–40[–50]-flowered, terminal or axillary, heads, globose to slightly elongated, solitary or clustered, sometimes in pseudoracemes or pseudopanicles; bracts present. Flowers mimosoid; calyx campanulate, lobes 5; corolla greenish white, drying pale pink, lobes 5; stamens 175–250, distinct, exserted, creamy white [yellow, pink]; anthers dorsifixed, eglandular; ovary short-stipitate, glabrous; style and stigma filiform. Fruits legumes, stipitate, flattened, straight, linear [oblong], usually dehiscent along sutures, glabrous. Seeds 3–15[–20], uniseriate, strongly flattened, ovate to orbiculate, not surrounded by pulp; pleurogram U-shaped. x = 13.
Distribution
sw, c, se United States, Mexico, Central America, s South America (Argentina).
Discussion
Species 15 (2 in the flora).
Acaciella has only recently come into common use following the division of Acacia in the broad sense into several genera, based on molecular studies (J. T. Miller and R. J. Bayer 2000; S. Gómez-Acevedo et al. 2010) and a revision by M. L. Rico-Arce and S. Bachman (2006). The following characteristics separate this genus from other members of Acacia in the broad sense (Acacia, Mariosousa, Senegalia, and Vachellia): absence of prickles and stipular spines, absence of petiolar and rachis nectaries, relatively numerous stamens (175–200+ per flower), and stalked flowers (usually in globose heads).
Selected References
None.
Lower Taxa
Key
| 1 | Leaflet blades 2–3.5(–4) × 0.5–1.3 mm, only midveins prominent abaxially. | Acaciella angustissima |
| 1 | Leaflet blades 4–13 × 1.5–3.1 mm, lateral veins and midveins prominent abaxially. | Acaciella lemmonii |