'' Acacieae (
Dumort., 1829) is a wide-ranging,
polyphyletic tribe of legumes in the Mimosoideae that is native to the
tropics, subtropics, and warm-temperate regions. It includes five or six genera and some 1,450 species. • Subdivision – 5 or 6 genera •
Acacia Mill. – type genus His Acacieae tribe of 1842 included many genera that were subsequently assigned to tribe Ingeae Benth. In 1875, however, Bentham narrowed his definition of Acacieae so as to include only
Acacia Mill. The only morphological character of Acacieae used to distinguish it from the Ingeae is the presence of free stamens (as in tribe Mimoseae). The tribal position of monotypic genus
Faidherbia A. Chevalier is equivocal. In the latter case, tribe Acacieae may conform to genus
Acacia s.l., pending the latter's relationship to other mimosoid genera.
Faidherbia is troublesome as its stamens are shortly united at their base and its pollen is similar to some taxa in the Ingeae. Where they have spines, these are modified stipules. In some, prickles arise from the stem's cortex and epidermis. The leaves are bipinnate or are modified to vertically oriented phyllodes. A few have cladodes rather than leaves.
Extrafloral nectaries may be present on the petiole and rachis, and the pinnule tips may carry protein-lipid
Beltian bodies. and the sap of various species hardens into gum. The inflorescences are dense pedunculate heads or spikes borne in axillary clusters, or are aggregated in terminal panicles. The tetra- or pentamerous flowers are uniformly bisexual, or male and bisexual. Sepals are connate (i.e. fused) and valvate (i.e. not overlapping). The reduced petals are valvate, or rarely absent. The flowers have numerous exserted (i.e. protruding) stamens (>2× as many as the corolla lobes), and their filaments are sometimes connate at their base (forming a short stemonozone). Male flowers of some
Neotropical species have a reduced staminal tube (cf.
A. albicorticata,
A. hindsii,
A. farnesiana, and
S. picachensis). Flowers are usually yellow or cream-coloured, but may be white, red, or purple. The ovary is sessile or stipitate (i.e. supported by a stipe), with many ovules or ovules arranged in two rows. The ovary is attached by a filiform style to a small, capitate stigma. The legume's endocarp is attached to the exocarp, but is otherwise very variable, and may be dehiscent or indehiscent. Seeds are usually elliptic to oblong and flattened to varying degrees. Seeds have a hard black-brown testa (i.e. seed coat) with a pleurogram, visible as a closed or almost closed O-shaped line. Some phyllodinous species have a colourful
aril or
elaiosome on the seed. ==References==