Acacia hindsii x A. cochliacantha

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 : 136-137

Acacia hindsii x A. cochliacantha .

Acacia x gladiata Saff ., J. Wash. Acad. Sei. 5: 359. 1915. Myrmecodendron gladiatum (Saff.) Britton & Rose , N. Amer. FI. 23: 92. 1928. TYPE: Mexico. Sinaloa: vicinity of Rosario , 1849, J. Gregg 1135 (holotype, MO; photo, F, NY; fragment and photo, US) .

Shrub or small tree to 4 m tall, twigs dark reddish brown, nearly glabrous. Stipular spines light brown to reddish brown, glabrous, flattened (sometimes oval in cross section), symmetrical, widely spreading with an angle of 160 to 180°, linear-lanceolate, constricted toward the base, to 60 mm long, 5-13 mm wide. Leaves 70-130 mm long; pinnae 8-16 pairs per leaf, 15-35 mm long, 5-10 mm between pinna pairs; rachis puberulent, a columnar gland with a depressed apex located near the node between each pinna pair (sometimes absent); petiole grooved, puberulent, 7-10 mm long. Petiolar glands columnar to volcano-shaped, 1-2 scattered along the petiole, glabrous, striate, apex 0.4-1.5 mm across. Leaflets 14-20 pairs per pinna, glabrous, linear, 2.5-4.5 mm long, 0.7-1.2 mm wide, one vein from the base, lateral veins not obvious. Inflorescence a loosely flowered, cylindrical spike, 8-17 mm long, 3.5-5 mm thick, in clusters of 2-6; peduncles to 13 mm long, puberulent; involucre located at or above the middle of the peduncle, 4-lobed, puberulent. Floral bracts spatulate. Flowers sessile; calyx 0.6-0.9 mm long, the lobes puberulent; corolla puberulent, maroon, 5-6-lobed, about twice as long as the calyx. Fruits not seen.

Representative specimens. MEXICO. Oaxaca: 3 mi. N of Puerto Escondido, Seigler et al. 11566 ( ILL) . Sinaloa: 14.4 mi. NW of Rosario on hwy. 15, Janzen 1720 ( EIU, ILL) , Ortega 4884 ( US) .

The narrow cylindrical inflorescences, the small leaflets, and the presence of rachis glands indicate that A. hindsii is the ant-acacia parent, while the enlarged, flattened stipular spines suggest that A. cochliacantha is the non-ant-acacia parent. In many of its characteristics this hybrid is intermediate between the parents. The large, compressed stipular spines are similar to those of A. cochliacantha , although these spines are not spoon-shaped as in typical A. cochliacantha . No specimens were found on which the spines exhibited the characteristic entrance holes made by acacia-ants. Overall, the leaves are similar to those of A. cochliacantha in that they are relatively short and narrow. The leaflets, however, are similar to those of A. hindsii , being 3.0- 4.5 mm long and 0.7-1.2 mm wide. In A. cochliacantha , in contrast, the leaflets are typically 0.8-2.4 mm long and 0.3-0.6 mm wide ( Seigler & Ebinger, 1988). Furthermore, the presence of rachis glands indicates a relationship to A. hindsii , as does the presence of Beltian bodies on the lower 1-4 leaflet pairs of most pinnae.