Description: This species of Acacia differs from others by the following
combination of characteristics: leaves bipinnate, flowers in spikes,
plants unarmed or only slightly thorny, the pinnae in (4)6-10
Distribution: Isely (1973) records this species from Arizona
and Mexico; Kearney and Peebles limit this general range slightly
by stating that the species occurs in southern Arizona and northern
Mexico. Wiggins (1964) indicate the species to be from Arizona,
Sonora and Chihuahua. Britton and Rose (1928) give the type locality
of this species [Senegalia millifolia (S. Wats.) Britt.
& Rose] as the Hacienda San Jose in Chihuahua. This may be
at the present San José de Babícora in western Chihuahua
about 300 km south of the Mexico-US border for this was an important
early collecting area, but without access to early literature
and knowledge of the collector's itinerary the site must remain
indefinite for the time being. Spellenberg et al. (1986) report
the species for the first time in extreme southwestern New Mexico
a few meters north of the Mexico-US border.
Plants Seen or Cited: New Mexico, Hidalgo Co.: Guadalupe
Canyon and tributaries in extreme SW corner of county, on & in
vicinity of Hadley Ranch, ca. 50 m N of Mexican border, ca. 1/2
mi E of Arizona, W edge S24, T24S, R22W, 17 Aug 1979, Spellenberg
& Repass 5371 (NMC). There are two sheets of this species
from Arizona at UTEP.
Habitat: Ledges, desert grassland, open rocky slopes,
foothills, 4,000-5,000 ft. (Isely 1973); generally igneous rock
with sparse oak, juniper, and Mexican pinyon on rocky hills (Spellenberg
& Repass 5371).
Discussion: Martin and Hutchins (1980) do not indicate that
this species might be expected in New Mexico. Isely (1973) notes
this species to be "locally abundant," his treatment
exclusively north of the Mexico-US border (thus he means in
Arizona). In contrast, Kearney and Peebles (1969) say that the
species is "apparently rare.". The following do not
record the species in their areas of concern: Estrada C. et al.
(1997) - Babícora region, Chihuahua; González E.
et al. (1991) - Durango; Henrickson and Johnston (1997) - Chihuahua
Desert region; Martin, Jenkens et al. (1990) - Río Mayo
region of Chihuahua and Sonora; Spellenberg et al. (1996) - Basaseachi,
Chihuahua. Thus, with information available at this time, the
extent of the range of the species can be ascertained only to
be restricted to the four states, Arizona, Sonora, Chihuahua,
and New Mexico, most likely in the lower Madrean vegetation region
in the northern Sierra Madre Occidental, but the extent of the
distribution cannot be determined except to suggest that it does
not extend as far south as central Chihuahua and adjacent Sonora. This is
apparently a regional endemic in the northern
Sierra Madrean area, apparently rare but locally common in southeastern
Arizona and extending into New Mexico in the southwestern corner
of the state by a very small distance.
Britton, N.L, and J.N. Rose. 1928. Mimosaceae (continuatio).
North American Flora 23(2): 77-136.
Estrada C., A.E., R. Spellenberg, and T. Lebgue. 1997. Flora
vascular de la Laguna de Babícora, Chihuahua, México.
Sida 17(4): 809-828.
González E., M.S. González E., Y. Herrera A. 1991.
Flora de Durango. Listados Florísticos de México,
IX. Instituto de Biología, Universidad Nacional Autónoma
de México, México. 167 pp.
Isely, D. 1973. Leguminosae of the United States: I. Subfamily
Mimosoideae. Mem. N. Y. Botanical Gard. 25(1): 1-150.
Kearney, T.H. and R.H. Peebles. 1969. Arizona Flora, 2nd
ed. (with supplement by J.T. Howell, Elizabeth McClintock, et
al.). Univ. California Press, Berkeley. 1085 pp.
Martin, P.C., P. Jenkins, and others. 1990. Manuscript checklist
of the plants of the Rio Mayo region in western Chihuahua and
southern Sonora. 351 mss pages (no authors indicated).
Spellenberg, R., T. Lebgue, and R. Corral-Díaz. 1996.
A specimen-based, annotated checklist of the vascular plants of
Parque Nacional "Cascada de Basaseachi" and adjacent
areas, Chihuahua, México. Listados Florísticos
de México, XIII. Instituto de Biología, Universidad
Nacional Autónoma de México, México. 72 pp.
Spellenberg, R., R. Worthington, P. Knight, & R. Fletcher.
1986. Additions to the flora of New Mexico. Sida 11(4):455-470.
Wiggins, I.L. 1964. Flora of the Sonoran Desert. Part II;
pp. 189-1699 in: F. Shreve and I.L. Wiggins, Vegetation
and Flora of the Sonoran Desert. Stanford Univ. Press, Standford.
2 vols, 1740 pp.
Information Compiled By: Richard Spellenberg 1998