Acacia gentlei Stand.

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 : 127

6. Acacia gentlei Stand. , Publ. Field Mus. Nat. Hist., Bot. Ser. 22: 77. 1940. TYPE: Belize. P. Gentle 185 (holotype, F) .

Small tree to 20 m tall; young twigs dark reddish brown, densely puberulent. Stipular spines dull, red to dark brown, most commonly black, usually lightly puberulent, terete, commonly symmetrical to slightly asymmetrical, U-shaped with an angle of 30 to 60°, suberect to recurved around the stem, 35-80 mm long, 3.5-6 mm thick near the base. Leaves 70-180 mm long; pinnae 5-12 pairs per leaf, 55-90 mm long, 13-20 mm between pinna pairs; rachis grooved, puberulent, a narrow, volcano-shaped gland located on the rachis internodes between each pinna pair; petiole grooved, densely puberulent, 9-20 mm long. Petiolar glands narrowly volcano-shaped, usually laterally compressed, solitary (rarely 2), puberulent, lightly striate, apex 0.6-1.2 mm across, base 2-3 mm long, located near the base to middle of the petiole. Leaflets 20-35 pairs per pinna, glabrous, linear, 7-14 mm long, 1.8-3.1 mm wide, lateral veins obvious, 3-5 veins from the base, apex obtuse to acute, margins ciliate. Inflorescence a densely flowered, cylindrical spike 15-40 mm long, 4-6 mm thick, nearly the same thickness throughout, apex blunt, in racemes on fertile branchlets with usually one (occasionally 2-4) spike at a node in the axil of a reduced leaf; peduncles puberulent, 16-22 mm long, 0.7-1.1 mm thick, nearly the same thickness throughout; involucre located near the middle of the peduncle, puberulent, 4-lobed with 2 lobes longer. Floral bracts peltate, apex circular, puberulent, the stalk less than 1 mm long. Flowers sessile; calyx 5-lobed, puberulent, 0.5-0.8 mm long; corolla 5-lobed, puberulent, yellowish, 1.3-1.8 mm long, twice as long as the calyx. Legumes straight to slightly curved, flattened, 160-300 mm long, 9-14 mm wide, glabrous, longitudinally striate, black to dark brown, dehiscent along both sutures, stipe 10-30 mm long, the apex narrowing to a spikelike beak 10-40 mm long. Flowering January-May.

Distribution. Rainforests, wet successional areas where the vegetation is 15-20 years of age, wet disturbed sites, swamps, and river edge vegetation in the lowlands of Belize, northern Guatemala, and extreme southern Mexico.

Representative specimens. BELIZE. 3-6 mi. S of Belmopan , Dwyer 12544 ( F, GH, MO) ; Southern Hwy., 14 mi. N of Punta Gorda, San Antonio , Gentry 8072 ( MEX, MO) ; Maskall , Gentle 1121 ( F, GH, MICH, MO, NY) ; Hummingbird Hwy. , Gentle 9078 ( F, MICH, MO, NY) ; Mountain Pine Ridge, Blancaneaux Lodge , Wiley 457 ( MO) . GUATEMALA. Alla Verapaz: along Rio Sebol between Sebol and Carrizal, N of Sebol , 200-300 m, Steyermark 45762 ( F) . Izabal: El Zapotillo, 1 km E El Estor (Lake Izabal) , Janzen 657 ( F, GH, MEX, MICH, MO, US) . El Petén: Uaxactun , Bartlett 12578 ( NY, TEX, UC) . Tikal National Park, Tikal, in ramonal , Ibarra 16 ( LL) . MEXICO. Chiapas: a 3 km al S de Frontera Corozal, sobre el Rio Usumacinta , 120 m, Martinez S. 11433 ( MEX, MO, NY) . Quintana Roo: a 2 km al N de Estero Franco, carretera Chetumal-La Union , Cabrera & Cabrera 2512 ( MEX, MO) . Tabasco: Carretera W-O por El Poblado de Apatzingan, Balancan , 150 m, Calzada 2345 ( F, MEX, MO) .

Acacia gentlei is a common species in wet sites at lower elevations in Belize, Guatemala, and extreme southeastern Mexico. It is distinguished easily from all other ant-acacias by the combination of its elongate inflorescence, laterally compressed, volcano-shaped glands scattered along the leaf rachis, very thin spines (usually less than 6 mm thick), and relatively large leaflets (7-14 mm long) with obvious secondary veins.

Unlike many of the wet forest ant-acacias, Acacia gentlei is a common species in areas of human disturbance. It appears as a successional species after logging, and in many parts of its range is found along roadsides. Unlike most wet forest ant-acacias, it has relatively large Beltian bodies (1-2 mm long) on most of the leaflets. Like most of the other ant-acacias, it usually lacks cyanogenic glycosides in the leaflets. Of the specimens examined, only one, Lundell 16903, from Guatemala, was weakly cyanogenic.