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Vachellia pringlei - leaves

Vachellia pringlei - spines on trunk

Vachellia pringlei

Vachellia pringlei

Vachellia pringlei

Vachellia pringlei

Vachellia pringlei

Vachellia pringlei - leaf

Name

Vachellia pringlei (Rose) Seigler & Ebinger, Phytologia 87:  165.  2005.
syn. Acacia pringlei Rose, contr. U. S. Natl. Herb. 3:  316.  1895.

Synonymy and types

Basionym:  Acacia pringlei Rose, Contr. U. S. Natl. Herb.  3: 316.  1895.  Acaciopsis pringlei (Rose) Britton & Rose N. Amer. Fl. 23: 95.  1928. - TYPE:  MEXICO.  OAXACA:  Tomellín Canyon, alt. 3000 ft. a tree 20-30 ft. high, 22 Dec 1894, C. G. Pringle 6113 (holotype:  US; isotypes:  CM, F, MO, UC).

Acacia unijuga Rose, Contr. U. S. Natl. Herb.  8: 32.  1903.  Acaciopsis unijuga (Rose) Britton & Rose, N. Amer. Fl.  28: 95.  1928. - TYPE:  MEXICO.  SAN LUIS POTOSÍ:  Las Palmas, lowlands, 9 Mar 1899, C. G. Pringle 6989 (holotype:  US; isotypes:  CM, F, LL, MO, UC).

Acacia conzattii Standl., Contr. U. S. Natl. Herb.  20: 186.  1919.   Acaciopsis conzattii (Standl.) Britton & Rose, N. Amer. Fl.  28: 95.  1928. - TYPE:  MEXICO.  OAXACA:  Estación Almaloyas, alt. 700 m, Mar 1907, C. Conzatti 1756 (holotype:  US).

Acaciopsis sesquijuga Britton & Rose, N. Amer. Fl.  28: 95.  1928.  Acacia sesquijuga (Britton & Rose) Standl., Field Mus. Nat. Hist. Bot. Ser.  3: 277.  1930. - TYPE:  MEXICO.  YUCATÁN:  Silam, G. F. Gaumer 1307 (holotype: MO).

Formal description

Tree to 15 m tall.  Bark dark gray to brown, shallowly furrowed.  Twigs dark purplish brown to dark gray, slightly flexuous, glabrous to lightly puberulent.  Short shoots commonly present above the stipular spines, to 8 mm long, covered with acuminate stipules and old leaf bases.  Leaves alternate, also commonly clustered on the short shoots, 4-30 mm long.  Stipular spines light to dark purplish brown, usually becoming light gray with age, symmetrical, terete, straight, thin, to 35 (50) x 1.5 (3.0) mm near the base, glabrous to lightly pubescent at the base.  Petiole adaxially grooved, 11-30 mm long, glabrous to pubescent; petiolar gland solitary, mostly located medially on the petiole, sessile, circular to elliptic, 0.8-1.8 mm long, apex depressed, glabrous to occasionally puberulent, sometimes absent.  Rachis absent.  Pinnae 1 pair per leaf, 15-35 mm long.  Petiolules 3-18 mm long.  Leaflets 2 (very rarely 3) pairs per pinna, subopposite to alternate, 5-18 mm between leaflets, ovate to obovate, terminal leaflets 10-40 x 9-30 mm, the lateral leaflets mostly smaller, glabrous to rarely lightly pabescent beneath, lateral veins obvious, 2 to 4 vein from the base, base oblique, margins usually ciliate, apex obtuse and usually mucronate.  Inflorescence a loosely flowered elongated spike, 30-130 mm long, solitary or in clusters of 2 to 8 on the short shoots.  Peduncles 0-6 x 0.6-0.9 mm, glabrous to densely puberulent.  Involucre usually 4-lobed, at the base of the peduncle, the lobe apex ciliate the remainder glabrous, persistent.  Floral bracts spatulate, 0.7-1.2 mm long, puberulent, deciduous.  Flowers sessile, white to cream-colored; calyx 4-lobed, 0.7-1.4 mm long, glabrous and striated; corolla 4-lobed, 1.5-2.0 mm long, glabrous or nearly so; stamen filaments 2.5-4.0 mm long, distinct; ovary glabrous, on a stipe to 0.4 mm long.  Legumes dark reddish brown, straight to slightly curved, flattened, sometimes slightly constricted between the seeds, linear, 60-200 x 5-8 mm, coriaceous, reticulately striate, glabrous, eglandular, dehiscent; a chartaceous pericarpicstrip lining each valve; stipe to 12 mm long; apexa cuminate and sometimes beaked.  Seeds uniseriate, no pulp, dark gray to dark brown, oblong, strongly flattened, 6.3-10.0 x 3.5-4.5 mm, smooth; pleurogram oblong to U-shaped, 1.1-2.0 mm across. Flowers in January to April. Chromosome number:  Not determined.

Distribution

From Yucatán through Oaxaca and Veracruz and north to San Luís Potosí and Tamaulipas.

Additional info

Vachellia pringlei is extremely variable morphologically.  As a result, Britton and Rose (1928), Standley (1922) and others have divided this taxon into three or four species.  These segregated taxa show some regional variation, but no significant differences exist when examined throughout its entire geographic range.  Most of the synonomy can probably be attributed to the small number of specimens available to the authors of these names.

The characteristics used to separate the synonyms as separate species (spine length, inflorescence length, and pubescence) varies extensive.  Typically specimens have short or no stipular spines, but sometimes spines are to 50 mm long. Also, most plants are nearly glabrous to lightly pubescent, but spines and twigs are rarely strongly pubescent, while the petioles are very rarely densely pilose, and the leaflets are rarely lightly pubescent beneath.  Leaflet size and shape and petiole length also varies widely, most of this variation being related to the difference in size of the primary leaves and the mostly smaller leaves that develop from the short shoots.

Vachellia pringlei is easily separate from V. californica by the presence of dense pubescence on both leaflets surfaces of V. californica.  Also, V. pringlei usually has much larger leaves with the terminal leaflets on the primary leaves consistently exceeding 25 mm.  On the short shoots, the leaves are generally smaller, but the terminal leaflets still commonly exceed 25 mm in length.

The authors have found many sterile specimens of Pithecellobium dulce (Roxb.) Benth. labeled Vachellia (Acacia) pringlei.  Superficially these taxa are similar, but can be consistently separate since P. dulce has a single pair of leaflets per pinna, and has a stalked petiolar gland between the pinna pair.  Vachellia pringlei, in contrast, has most leaves with 2 pairs of leaflets per pinna, and the petiolar gland is sessile and commonly near the middle of the petiole.

Of the 68 specimens of this species tested for cyanide production, six gave a weakly positive test (Lee et al. 1898).  Emulsin was added before a positive test was obtained, suggesting that the cyanogenic glycoside is sometimes present, but that the enzyme is not usually produced by the plant.

Flowering time

January-July.

Vachellia pringlei:

January-April.

Representative specimens

MEXICO:

Chiapas:

Jalisco:

Michoacán:

Oaxaca:

Puebla:

Quintana Roo:

San Luís Potosí:

Tamaulipas:

Veracruz:

Yucatán:

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