Name
Vachellia farnesiana (Linnaeus) Wight & Arnott var. minutum (M. E. Jones) Seigler & Ebinger, Phytologia 87:157. 2005. syn. Acacia farnesiana (L.) Willd. subsp. minuta (M. E. Jones) Ebinger & Seigler, Southw. Naturalist 47:90. 2002.
Synonymy and types
Basionym: Pithecellobium minutum M. E. Jones, Contr. W. Bot. 18:38. 1933. - Acacia minuta (M. E. Jones) R. M. Beauch., Phytologia 46:5. 1980. - Acacia farnesiana (L.) Willd. subsp. minuta (M. E. Jones) Ebinger & Seigler, Southw. Naturalist 47:90. 2002. - TYPE: MEXICO. BAJA CALIFORNIA: Cacachilla Mts., 2 Oct 1930, M.E.Jones 27265 (holotype: POM-RSA).
Formal description
Large shrub to small tree 8 m tall. Bark dark gray to brown, furrowed. Twigs dark reddish brown to dark gray, slightly flexuous, usually glabrous. Short shoots commonly present above the stipular spines, to 10 mm long, covered with acuminate stipules and old leaf bases. Leaves alternate, also commonly clustered on the short shoots, mostly 15-30 mm long. Stipular spines light to dark brown, usually becoming light gray with age, symmetrical, terete, straight, stout, to 35(55) x 1.5 mm near the base, mostly glabrous. Petiole adaxially grooved, 6-15 mm long, usually densely pubescent with erect hairs; petiolar gland solitary, usually located medially on the petiole, sessile to short stalked, circular to slightly elongated, 0.2-1.0 mm long, apex depressed, glabrous. Rachis adaxially grooved, 10-55 mm long, usually sparsely pubescent with erect hairs, a sessile, circular gland, 0.2-0.4 mm across, between the upper 1 to 2 pinna pairs. Pinnae 2 to 4(5) pairs per leaf, 15-20 mm long, 2-12(16) mm between pinna pairs. Petiolules 0.5-2.0 mm long. Leaflets 8 to 19 pairs per pinna, opposite, 0.5-2.0 mm between leaflets, oblong, 3.0-6.3 x 0.5-1.7 mm, pubescent beneath, lateral veins usually obvious, only one vein from the base, base oblique, margins usually not ciliate, apex broadly acute to obtuse. Inflorescence a densely flowered globose head, 6-10 mm across, solitary or in clusters of 2 to 5 on the short shoots. Peduncles 12-36(45) x 0.2-0.7 mm, lightly puberulent. Involucre 4- to 5-lobed, located at the base of the globose head, glabrous to lightly puberulent, persistent. Floral bracts spatulate, 0.8-1.3 mm long, apex puberulent, deciduous. Flowers sessile, bright yellow; calyx 5-lobed, 1.1-1.8 mm long, glabrous or nearly so; corolla 5-lobed, 1.9-2.8 mm long, glabrous or nearly so; stamen filaments 3.5-5.5 mm long, distinct; ovary glabrous to puberulent, on a stipe to 0.2 mm long. Legumes dark brown to black, straight to slightly curved, nearly terete in cross section, not constricted between the seeds, oblong, 100-170 x 9-18 mm, coriaceous, reticulately striate, glabrous, eglandular, indehiscent; stipe to 7 mm long; apex obtuse to acuminate, sometimes beaked. Seeds uniseriate, imbedded in a sweet pulp, olive green to dark brown, ovoid to ellipsoid, slightly flattened, 4.2-8.0 x 3.5-5.8 mm, smooth; pleurogram U-shaped to oval, 2.5-4.5 mm across. Flowers from December to May. Chromosome number: Not determined.
Distribution
Chaparral, dry thorn -scrub and disturbed habitats from sea level to 1500 m from southern California (San Diego Co.) south through Baja California, Mexico.
Additional info
Vachellia farnesiana var. minuta has a very restricted range in Baja California of Mexico and adjacent California, where it is sympatric with V. farnesiana var. farnesiana. Fruit length in excess of 100 mm, and the uniseriate seeds consistently separate it from the other subspecies of V. farnesiana. Also, its erect habit, being a large shrub or small tree, separates it from V. farnesiana var. pinetorum, a nearly prostrate to weakly erect shrub to 1.5 m tall, that is restricted to southern Florida. Besides fruit characteristics, the larger leaflets separate this taxon from V. farnesiana var. pinetorum, while the usually few pinnae pairs, and the shorter pinna (mostly less than 20 mm long) are helpful in separating this subspecies from V. farnesiana var. farnesiana. The only completely reliable characteristic however is the longer, uniseriate fruits.
Herbarium labels indicate that Vachellia farnesiana var. minuta is mostly associated with arroyos, and other areas where water sometimes accumulated. Also, it is associated with disturbances, and most populations from San Diego Co., California are from roadsides and other disturbance sites. It is very possible that its occurrence in California is the result of past introductions, probably before the time of settlement by Europeans. Of the more than 40 specimens examined for cyanogenic glycosides, all gave a negative reaction even after the addition of emulsin.
Flowering time
December - May.
Representative specimens
UNITED STATES:
California:
San Diego Co.:
- 2 miles S of Otay P. O., 2 Jan 1934, F.F.Gander s.n. (RSA, SD);
- 4.5 miles E of Del Mar, 27 Feb 1936, F.F.Gander 675 (SD);
- Federal Blvd, near Emerald Hills Club-house, 29 Jan 1935, F.F.Gander 1132 (SD);
- S of Otay, 18 Dec 1953, C.F.Harbison s.n. (SD);
- S of Otay, 29 Jun 1961, C.F.Harbison s.n. (RSA);
- Otay Mesa, 21 Nov 1950, E.B.Higgins s.n. (RSA);
- near radio station in San Diego, 1 Feb 1952, E.B.Higgins s.n. (RSA);
- near radio station, 2 Feb 1952, E.B.Higgins s.n. (RSA);
- S of Otay on highway, 5 May 1935, D.F.Howe 209 (SD);
- Balboa Park, San Diego, Jan 1945, C.I.Jerabek s.n. (SD);
- creek below old Rose place, Beyer Way, Otay, 10 Mar 1976, B.Mackintosh s.n. (SD);
- Beyer Way, Vista Ave. and Coronado Ave, 2 miles S of Otay, alt. 10 m, 13 Feb 1972, R.Moran 19077 (SD);
- arroyo bed in South Chollas Valley, S of hwy. 94 at Kelton Road, San Diego, alt. 70 m, 18 Apr 1972, R.Moran 19084 (SD);
- S of Otay, 30 Aug 1937, J.Roos 2560 (RSA);
- SW of Otay Valley, 6 Dec 1937, A.J.Stover s.n. (SD);
- on the road to Tia Juana, alt. 70 m, 31 Aug 1933, C.B.Wolf 5411 (RSA);
- 1 mile SW of Otay on the road to Tia Juana, alt 70 m, 26 May 1931, C.B.Wolf 2094 (RSA);
MEXICO:
Baja California:
- 1/2 mile W of San Telmo, alt. 500 ft., 28 Apr 1950, L.Benson 14329 (RSA);
- Misión Santa Gertrudis, 18 Dec 1950, A.Carter & L.Kellogg 2960 (SD);
- slopes behind village of Bahía de Los Angeles, alt. 500 ft.,16 Feb 1963, R.S.Cowan 2313 (SD);
- Caluealli, 6 Feb 1935, C.Epling & W.Robison s.n. (F, ILL, RSA);
- between Santo Tomas valley and San Vicente, 1 Mar 1934, R.S.Ferris 8508 (RSA);
- Las Juncas Rancho, 20 Apr 1940, C.F.Harbison s.n. (RSA, SD);
- Santa Gertrudis, 24 Apr 1940, C.F.Harbison s.n. (SD);
- Santa Gertrudis, 3 Dec 1953, C.F.Harbison s.n. (RSA);
- San Telmo, 17 Dec 1953, C.F.Harbison & E.B.Higgins s.n. (RSA);
- 0.4 miles NE of Pozo Alemán, alt. 290 m, 13 Oct 1971, J.R.Hastings & R.M.Turner 71-101 (SD);
- 2.4 miles below San Telmo, alt. 60 m, 1 Jul 1972, R.Moran 19167 (SD);
- N bank of Tijuana River, NE edge of La Mesa, alt. 50 m, 16 Feb 1975, R.Moran 21606 (MO, SD);
- 6 miles NW of San Vicente, alt. 140 m, 4 May 1980, R.Moran 28425 (SD);
- 6 miles NW of San Vicente, alt. 150 m, 15 Mar 1981, R.Moran 29481 (SD);
- 10 miles NW of San José del Cabo, alt. 300-600 ft., 2 May 1959, J.H.Thomas 7769 (SD);
- road to Sierra San Pedro Martir near San Telmo, 7 May 1986, R.F.Thorne, T.S.Elias & P.Rojas 61920 (NY);
Baja California Sur:
- Agua Verde Bay, 16 Mar 1949, E.Y.Dawson 6248 (RSA);
- San José del Cabo, 18 Jan 1923, M.E.Jones 24013 (F, MO, RSA, SD);
- Bahía de los Angeles, alt. 50 m, 4 Mar 1966, R.Moran 12414 (RSA, SD);
- 0.7 miles E of Santo Domingo, alt. 50 m, 20 Jan 1973, R.Moran 19537 (SD);
- S slope of Cerro la Laguna, N of Rcho, la Laguna, Sierra San Francisco, alt. 1340 m, 24 Nov 1976, R.Moran 23840 (SD);
- San Andrés, NW of Asunción, alt. 95 m, 5 Feb 1973, R.Moran & J.L.Reveal 19804 (SD);
- Agua Verde Bay, 10 Mar 1937, P.J.Rempel 126 (RSA);
- 3 km N of San Bartolo, on hwy. 1, 19 Jun 1981, D.S.Seigler & P.M.Richardson 11774 (EIU);
- 3 km W of San José del Cabo, 20 Jun 1981, D.S.Seigler & P.M.Richardson 1781 (EIU);
- 12.3 miles N Cabo San Lucas on road to Todos Santos, 15 May 1980, M.J.Warnock 2079 (TEX);