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8. Acacia hindsii Benth ., London J. Bot. 1: 504. 1842. Myrmecodendron hindsii (Benth.) Britton & Rose, N. Amer. FI. 23: 91. 1928. TYPE: Mexico . Jalisco : shore of Manzanilla Bay , sea level , 1841 , R. B. Hinds248 ( holotype , K , photo, F) .
Acacia bursariaSchenck , Repert. Spec. Nov. Regni Veg. 12: 363. 1913. TYPE: Guatemala . Amatitlán : Laguna Amatitlan , 3900 ft ., Feb. 1890 , J. D. Smith2304 ( lectotype , designated here, US [B destroyed];isotypes, GH,K) .
Acacia tepicana Saff ., J. Wash. Acad. Sei. 4: 366. 1914. TYPE: Mexico . Nayarit : thickets, vicinity of Acaponeta , Tepic , 30 m , 10 Apr. 1910 , J. N. Rose , P. C. Standley & P. G. Russell14357 ( holotype , US , photo, F;isotype, NY) .
Acacia sinaloensis Saff ., J. Wash. Acad. Sei. 4: 365. 1914. TYPE: Mexico . Sinaloa : vicinity of Villa Union , growing about a pond, 2 Apr. 1910 , J. N. Rose , P. C. Standley & P. G. Russell13972 ( holotype , US ; isotype, NY) .
Tree to 10 m tall; young twigs reddish brown to dark brown, glabrous to rarely lightly puberulent. Stipular spines (Fig. 1 C ) shiny, light brown to nearly black (sometimes light gray), smooth, glabrous to lightly puberulent, flattened at the base, symmetrical, nearly flat to broadly U-shaped across the top at an angle of 90-180°, 30-55 mm long, 10-20 mm wide at the base. Leaves 45-180 mm long; pinnae 10-18 pairs per leaf, 20-45 mm long, 6-12 mm between pinna pairs; rachis grooved, usually puberulent, a small narrow volcano-shaped gland located at the node between each pinna pair; petiole grooved, usually densely puberulent, 7-14 mm long. Petiolar glands narrow volcano-shaped (to almost columnar), usually 3-7 (rarely 1) scattered along the petiole, puberulent, lightly striate, apex 0.4-0.7 mm long, base 0.8-1.2 mm long. Leaflets 12-30 pairs per pinna, glabrous, linear, 3-7 mm long, 0.9-1.4 mm wide, one vein from the base, lateral veins not obvious, apex obtuse, margins lightly ciliate. Inflorescence a loosely flowered, cylindrical spike, 20-50 mm long, 4-7 mm thick, nearly the same thickness throughout, apex blunt, in racemes with 1-3 (rarely 4-8) spikes at each node in the axil of a reduced leaf; peduncles glabrous to lightly puberulent, 10-20 mm long, 0.6-1.1 mm thick, nearly the same thickness throughout; involucre located at the base to the lower third of the peduncle, puberulent, 4-lobed with 2 lobes longer. Floral bracts peltate, apex circular, stalk 0.4-0.7 mm long. Flowers sessile; calyx 5-lobed, puberulent, 0.5-0.9 mm long; corolla 5-6-lobed, puberulent, yellowish, 1.6-2.0 mm long, usually more than twice as long as the calyx. Legumes curved, elliptical in cross section, 40-100 mm long, 8-12 mm wide, glabrous to lightly puberulent, usually not striate, black to dark brown, dehiscent along one suture, short stalked, base narrowly cuneate, the apex narrowing to a beak 10-15 mm long. Flowering January-July.
Distribution. Disturbed, usually wet sites of the Pacific lowlands and foothills from extreme southern Sinaloa, Mexico, south to Nicaragua.
Representative specimens. EL SALVADOR . La Union : vicinity of La Union , 150 m or less, Standley20663 ( NY , UC , US ) . San Vicente : vicinity of Apastepeque ,, Standley21333 ( NY ) . Sonsonate : vicinity of Acajutla , 30 m or less, Standley21942 ( US ) . GUATEMALA . Alta Verapaz : near Pancajche , about 360 m , Standley70648 ( F ) . Escuintla : S of Rio Burrion, NE of Escuintla , about 700 m , Standley89619 ( F ) . Retalhuleu : vicinity of Retalhuleu , 240 m , Standley88846 ( F ) . San Marcos : Sands, Ocos , 1-2 m , Steyermark37779 ( F ) . HONDURAS . Encinales del Valle de El Espinocerca de San Jeronimo , 350 m , Molina R. 8059 ( F , MO , US ) . MEXICO . Chiapas : 13 mi . NE of the border of Chiapas & Oaxaca on hwy. 190 , Seigler et al.11583 ( ILL ) . Colima : Manzanillo , Palmer1395 ( MO , NY , US ) . Guerrero : sandy river bank, Tecpan- El Verde , 20 m , Hinton14120 ( MO , TEX , US ) . Jalisco : just E of Barra de Navidad in sandy soil near sea level , in thickets about margin of palm forest, McVaugh11847 ( US ) . Michoacán : a 10 kmaprox . al N de-Playa Azul , carr . a NuevaItalia , Nunez & Boom 2115 ( MO ) . Nayarit : 4 mi . S of intersection to Acaponeta on hwy. 15 , Seigler et al.11797 ( ILL ) . Oaxaca : sand dunes behind the beach at Salina Cruz , King2461 ( TEX , US ) . Sinaloa : near Colomas , in the foothills of the Sierra Madre , Rose1766 ( NY ) .
Like Acacia collinsii and A. cornigera , A. hindsii has an extensive geographical range. Unlike these species, however, A. hindsii is restricted to the Pacific lowlands and foothills in Central America. Before the existence of extensive agriculture in the region it was probably common along rivers, in semideciduous and deciduous forests, and in mangrove swamps (Janzen, 1974). Presently it is a common element of shrubby regeneration, particularly in wetter habitats such as river banks, where it commonly forms dense thickets by means of root sprouts.
Acacia hindsii is easily separated from all other ant-acacias by its stipular spines, which are flattened at the base and nearly flat to broadly U-shaped across the top. It is morphologically very similar to A. collinsii and A. gentlei , both of which have relatively small leaves and cylindrical spikes, but differs in leaflets that lack obvious secondary venation.
As is typical of most ant-acacias that inhabit more open sites, Beltian body production in Acacia hindsii is relatively extensive. In this species the small, slightly elongated Beltian bodies usually are less than 1 mm long, and are found commonly on more than 60% of the leaflets of developing leaves. As most individuals of this species are inhabited by obligate acacia-ants, the Beltian bodies generally are not seen, being “harvested” soon after development.
Acacia hindsii is polymorphic with respect to HCN production (Seigler & Ebinger, 1987), being reported acyanogenic by Rehr et al. (1973), while Seigler et al. (1978) found individuals that are strongly cyanogenic. Of more than 300 herbarium specimens tested, 123 were positive for HCN production. In general, many of the specimens from Mexico tested positive for cyanide, while most of the acyanogenic specimens are from Guatemala, El Salvador , and Honduras. The glycoside in this species is proacacipetalin .
Acacia hindsii probably hybridizes with the ant-acacia A. collinsii . It also has been reported to hybridize with non-ant-acacias of the A. macracantha complex, particularly A. pennatula ( Acacia x standleyi Safford ), and A. cochliacantha ( Acacia x gladiataSafford ).