Vachellia cookii (Safford) Seigler & Ebinger, Phytologia 87:  153.  2005.
syn. Acacia cookii Safford, Science N. S. 31:  677.  1910.

Synonymy and types

Acacia cookii Saff., Science N.S. 31:677. 1910. - Mymecodendron cookii (Saff.) Britton & Roze, N. Amer. FI. 23:93. 1928. - TYPE: Guatemala, ALTAVERAPAZ. Finca Trece Aguas, near Secangain, alt. 300m, 8 Mar. 1987, G.P. Goll 102 (holotype: US).

Acacia bucerophora B. L. Rob., Proc. Amer. Acad. Arts   49: 502.  1913. - TYPE:  BELIZE.  Belize, about Toledo, 4 mi. from the coast and 5 miles from Punta Gorda, sea level, 29 Mar 1907, M. E. Peck 632 (holotype:  GH, F fragment and photo, US fragment and photo; isotypes:  F, K).

Formal description

Tree to 12 m tall.  Bark not seen.  Twigs dark reddish brown to black, not flexuous, densely puberulent.  Short shoots absent.  Leaves alternate, 275-500 mm long.  Stipular spines dark brown to black, asymmetrical, terete, usually curved around to stem, stout and inflated, 60-100 x 3.5-5.5 mm near the base, densely puberulent.  Petiole adaxially grooved, 9-16 mm long, densely puberulent; petiolar gland solitary, extending nearly along the entire length of the petiole and lower than the top of the groove, sessile, the elongated apex 6-13 mm long, base 6-13 mm long, glabrous to lightly puberulent.  Rachis adaxially grooved, 250-480 mm long, densely puberulent, a sessile, elongated gland, 1-3 mm long, between each pinna pair.  Pinnae 18 to 40 pairs per leaf, 60-85 mm long, 10-15 mm between pinna pairs.  Petiolules 1-2 mm long.  Leaflets 50 to 70 pairs per pinna, opposite, 0.7-1.3 mm between leaflets, linear, 6-8 mm x 0.9-1.2 mm, glabrous, lateral veins not obvious, only one vein from the base, base oblique, margins not ciliate, apex acute; beltian bodies 1-2 mm long.  Inflorescences of densely flowered globose heads, 6-8 mm across, in axillary clusters of 20 to 70 subtended by normal to slightly reduced leaves.  Peduncles 15-30 x 0.8-1.2 mm, glabrous to lightly puberulent.  Involucre 4- to 7- lobed, located near the middle of the peduncle, glabrous to lightly puberulent, persistent.  Floral bracts peltate, 0.8-1.1 mm long, apex circular and ciliate, deciduous.  Flowers sessile, pale yellow; calyx 5-lobed, 1-1.3 mm long, glabrous; corolla 5-lobed, 1.5-1.8 mm long, about 1/3 longer than the calyx, glabrous; stamen filaments 1.8-2.7 mm long, distinct; ovary glabrous, on a stipe to 0.1 mm long.  Legumes bark brown to black, slightly curved, elliptical in cross section, not constricted between the seeds, linear, 250-300 x 10-16 mm, coriaceous, not striate, glabrous to lightly puberulent, eglandular, dehiscent along both sutures; stipe 10-40 mm long; apex narrowing to a terminal beak 10-30 mm long.  Seeds uniseriate, imbedded in a light brown pulpy material, light to dark brown, ellipsoid to ovoid, slightly flattened, 11.0-12.6 x 6.8-8.0 mm, smooth; pleurogram not seen.  Flowers in November to April. Chromosome number: Not determined.


In human and naturally disturbed sites along rivers and in wet forests with a very mild dry season, from sea level to 400 m elevation, in Belize and Guatemala.

Additional info

Vachellia cookii is separated easily from other ant-acacias by its thin, asymmetrical, densely puberulent stipular spines that are curved around the stem.  The only other species with similar spines, V. janzenii, is probably its nearest relative.  Though similar, plants of these two species are easily separated.  The stipular spines of V. cookii are long (60-100 mm), fairly thin (3.5-5.5 mm), and densely puberulent with short gray hairs.  Vachellia janzenii, in contrast, has shorter (30-60 mm), relatively broad (6-9 mm) stipular spines that are densely pubescent with straight, yellowish hairs to 0.5 mm long.  In V. cookii, the puberulent petioles are 9-16 mm long with a gland to 13 mm long, whereas in V. janzenii the pubescent petioles are less than 8 mm long and lack a gland.  The rachis glands that are located between each pair of pinnae also differ in these two species, being elongate (1-3 mm) in V. cookii and much smaller (0.5-0.7 mm) and circular in V. janzenii.  Further, the leaflets of V. cookii are 6-8 mm long, usually more than 1 mm wide and have glabrous margins, whereas in V. janzenii they are shorter (3-5.5 mm), narrower (0.6-0.9 mm) and have ciliate margins.  The arrangements of the inflorescences also differ. In V. cookii, the inflorescences are in axillary clusters of 20 to 70 on typical branches and are subtended by normal to slightly reduced leaves.  In V. janzenii, some of the inflorescences are on thin fertile branchlets to 250 mm long with 16 to 42 inflorescences in each of 6 to 12 fascicles that are usually not subtended by leaves (Ebinger & Seigler 1987, Seigler and Ebinger 1995).

Originally, Vachellia cookii was probably a wet forest species found in naturally disturbed sites along rivers in very wet forests (Janzen 1974), but is now associated with sites of human disturbance. Like those of most wet forest ant-acacias, specimens of V. cookii generally have relatively low Beltian body production with only the lower 6 to 12 pairs of leaflets on a pinna producing Beltian bodies.  As in most ant-acacias, none of the specimens of this species tested positive for cyanide production (Seigler and Ebinger 1995).

Flowering time


Representative specimens



Alta Verapaz: