10. Acacia mayana Lundell, Publ. Carnegie Inst. Wash. 478: 210. 1937. type: Guatemala. El Petén: near San Diego on the Rio Pasión, 10 Apr. 1935, M. Aguilar H. 495 (holotype, MICH; isotypes, GH, NY, US).

Shrub or small tree to 10 m tall; young twigs gray to light brown, glabrous. Stipular spines shiny, dark black, glabrous, symmetrical, V-shaped with an angle of 70 to 150°, the upper half strongly reflexed, 30-75 mm long, 5-12 mm thick near the base, two bladelike longitudinal flanges extending from the base to the apex along each side of the spine. Leaves 150-400 mm long; pinnae 6-19 pairs per leaf, 75-120 mm long, 15-30 mm between pinna pairs; rachis grooved, glabrous to puberulent, a small, elongated gland present between each pinna pair; petiole grooved, glabrous to puberulent, 15-35 mm long. Petiolar glands canoe-shaped, solitary (rarely 2), glabrous, striate on the sides, apex 1.2-5 mm long, located just below the first pinna pair. Leaflets 25-40 pairs per pinna, glabrous, linear, 10-23 mm long, 1.8-3.5 mm wide, lateral veins obvious, 3-5 veins from the base, apex obtuse. Inflorescence a densely flowered spike, 30-50 mm long, 7-10 mm near the base, narrowing toward the elongated and pointed apex, solitary or in small racemes on short, leafless, axillary branches; peduncles glabrous, 5-15 mm long, 4-6 mm thick, nearly the same thickness throughout; involucre located near the base of the peduncle, glabrous to lightly puberulent, with 4-5 irregular, shallow lobes. Floral bracts peltate, apex circular, the stalk 0.9-1.2 mm long. Flowers sessile; calyx shallowly 5-lobed, glabrous, 0.9-1.2 mm long; corolla 5-lobed, glabrous, pinkish, 1-1.3 mm long, only slightly longer than the calyx. Legume slightly curved, nearly terete, 90-120 mm long, 12-15 ihm thick, glabrous, longitudinally striate, dark reddish brown, indehiscent, stipe to 25 mm long, the apex narrowing to a long spinelike beak 7-20 mm long. Flowering January-June.

Distribution. Apparently a species of lowland, wet forests and forest margins in the departments of Alta Verapaz and El Petén, Guatemala, and the states of Chiapas, Oaxaca, Tabasco, and Veracruz, Mexico.

Representative specimens. GUATEMALA. Alta Verapaz: along Rio Icuolay, N and NW of Finca Cubil- guitz to Quebrada Diablo, 300-350 m, Steyermark 44726 (F). El Petén: high forest in zapotal & corozal, Chinchila, Sebol road, Contreras 10691 (F). MEXICO. Chiapas: near Lacanjá, Mpio. Ocosingo, Breedlove 34505 (MEX). Oaxaca: San Felipe, a 7 km al N-NW de Macedonio Alcala, Distr. de Tuxtepec, 80 m, Sousa et al. 7286 (MEX, MICH, NY). Tabasco: Retiro, above Tenosique, in virgin forest, Matuda 3410 (F, GH, LL, MEX, MICH, MO, NY). Veracruz: Estación de Biologia Tropical Los Tuxtlas, 200 m, Ibarra M. 1449 (MO, NY).

According to Janzen (1974), Acacia mayana probably represents a "wet-forest edition" of A. cornigera. Undoubtedly, the two taxa are very closely related, having many vegetative and floral characteristics in common. However, the large leaflets (more than 10 mm long), the rachis glands between each pinna pair, and the inflorescence, which narrows toward the elongated and pointed apex, separate this species from the closely related A. cornigera and A. sphaerocephala. Also, the pair of bladelike longitudinal flanges extending from the spine base to apex separates A. mayana from all other species of ant-acacia.

Acacia mayana is one of the rarest of the ant-acacias. Collecting data from the few collections observed indicate that it has pinkish flowers and varies in size from a shrub to a small tree to 10 m tall. Most collections indicate that it occurs as widely scattered individuals in moist lowland forests. Janzen (1974) reported an individual from an old second growth cornfield regeneration where the forest was about 15 m tall.

Unlike most wet forest ant-acacias, Beltian body production in Acacia mayana is extremely high. On developing leaves, nearly all of the leaflets contain Beltian bodies, and these bodies are usually about 2 mm long and up to 0.8 mm wide. As is typical of most ant-acacias, none of the individuals of A. mayana tested positive for cyanide production.