Acacia cornigera? x A. pennatula

David S. Seigler & John E. Ebinger, 1995, Taxonomic Revision of the Ant-Acacias (Fabaceae, Mimosoideae, Acacia, Series Gummiferae) of the New World, Annals of the Missouri Botanical Garden 82, pp. 117-138 : 136

Acacia cornigera? x A. pennatula : Small shrub to 2 m tall; twigs reddish brown, puberulent. Enlarged stipular spines light grayish brown, puberulent, terete to oval in cross section, symmetrical, straight, V-shaped with an angle of 80-160°, to 30 mm long, 3-4 mm wide near the base, most spines not enlarged, puberulent, less than 4 mm long. Leaves 70-120 mm long; pinnae 12-23 pairs per leaf, 22-34 mm long, 2-5 mm between pinna pairs; rachis puberulent, a nearly circular columnar gland with a depressed apex located near the node between each pinna pair; petiole grooved, puberulent, 4-7 mm long. Petiolar glands columnar, the apex depressed, usually 1 just below the first pinna pair, puberulent, lightly striate, apex 0.8-1.2 mm long. Leaflets 15-26 pairs per pinna, lightly puberulent, ciliate, linear, 2.2-4.5 mm long, 0.6-1.3 mm wide, one vein from the base, lateral veins usually not obvious. Flowers and fruits not observed.

Representative specimen. MEXICO. Veracruz: 24.3 mi. from Veracruz on hwy. 140, Seigler et al. 12224 ( ILL) .

The wide-ranging ant-acacia Acacia cornigera may rarely hybridize with the non-ant-acacia A. pennatula . The only specimen seen of this probable hybrid was a 2-m-tall sapling collected in a pasture where both parent species were common. The only other acacia species present was Acacia macracantha . The dense pubescence of this hybrid, however, suggests that A. pennatula is the non-ant-acacia parent. Not only are the twigs and spines densely puberulent, but the leaflets are lightly puberulent and ciliate, while the columnar rachis glands with a depressed apex are similar to those found in A. pennatula . The enlarged spines, the presence of Beltian bodies on the lower 1-2 leaflets of some pinnae, and the well-developed rachis and petiolar glands indicate a relationship to an ant-acacia species. Because A. cornigera is the only ant-acacia known to occur in this part of Mexico, it is probably the ant-acacia parent. However, the relatively small leaflets generally lack secondary veins, and the petiolar glands differ from the canoe-shaped glands of typical A. cornigera . Final determination must await flowering and fruiting material ( Ebinger & Seigler, 1992).