Name

Mariosousa millefolia (S. Watson) Seigler & Ebinger

Synonymy and types

Acacia millefolia S. Watson, Proc. Amer. Acad. Arts 21:427. 1886. - Senegalia millefolia (S. Watson) Britton & Rose, N. Amer. Fl. 23:111. 1928. - TYPE: Mexico, Chihuahua, Hacienda San Jose, near Batopilas, Aug. 1885, E.Palmer 45 (holotype: GH!, isotypes: MEXU!, NY!).

Formal description

Shrub or small tree to 3 m tall. Bark gray, smooth when young, becoming fissured into square plates 1-2 cm across. Twigs light brown to greenish brown, not flexuous, usually lightly puberulent. Short shoots absent. Leaves alternate, 60-230 mm long. Stipules herbaceous, light brown, narrowly linear, to 6.5 x 0.5 mm near the base, usually glabrous, persistent. Petiole adaxially grooved, 30-75 mm long, usually glabrous; petiole gland absent. Rachis adaxially grooved, 50-190 mm long, glabrous to lightly pubescent; a stalked gland with a globose apex, 0.3-0.9 mm across, between the pinnae of the upper 1 to 2 pinna pairs. Pinnae (2)6 to 14 pairs per leaf, 30-55 mm long, 10-28 mm between pinna pairs. Petiolules 2.0-4.0 mm long. Leaflets 20 to 35(37) pairs per pinna, opposite, 0.8-1.6 mm between leaflets, oblong, 2.0-6.5 x 0.7-1.4 mm, glabrous above, lightly pubescent beneath with appressed hairs, lateral veins not obvious, only one vein from the base, base oblique, margins sometimes ciliate, apex acuminate. Inflorescence a loosely flowered cylindrical spike 30-75 mm long, solitary (rarely 2 to 3), from the leaf axil. Peduncle 5-15 x 0.3-0.8 mm, glabrous to lightly puberulent. Involucre absent. Floral bracts linear, to 1.3 mm long, glabrous to lightly pubescent, early deciduous. Flowers sessile, creamy-white; calyx 5-lobed, 1.1-1.6 m long, glabrous; corolla 5-lobed, 2.0-2.7 mm long, glabrous; stamen filaments 4.5-6.5 mm long, distinct; ovary glabrous, on a stipe to 0.4 mm long. Legumes light yellowish brown, straight, flattened, not constricted between the seeds, oblong, 70-170 x 12-21 mm, chartaceous, irregularly striate, glabrous, eglandular, dehiscent along both sutures; stipe to 12 mm, apex acute to obtuse. Seeds uniseriate, no pulp, dark brown, nearly circular, strongly flattened, 6.2-9.5 mm across, smooth; pleurogram U-shaped, 2-3 mm across. Flowers: June-August. Chromosome number: Not determined.

Distribution

Desert grasslands, rocky slopes, subtropical scrub, and open oak woodlands from 700 to 1700 m elevation in southern Arizona, south through Sonora to western Chihuahua, Mexico.

Additional info

A shrub to small tree, usually less than 2 m tall, Mariosousa millefolia is relatively common in desert grassland and desert scrub vegetation in extreme southern Arizona and adjacent Sonora, Mexico. Commonly collected along the steep sides and floors of canyons, M. millefolia is rarely a dominant member of the vegetation, most collections indicating scattered individuals. Though numerous specimens are available from throughout most of the geographic range of this taxon, no specimens, other than the type collection, is known from Chihuahua. This taxon may be extremely rare in southwestern Chihuahua, or it is possible that the collecting data on the type specimens is incorrect. This collection, which was designated as the lectotype by Isley (1969), is more than 100 km east of any specimens of M. millefolia seen by the present authors.

Mariosousa millefolia is distinct from other members of this genus, as it lacks a petiolar gland and possess a stalked rachis gland between the upper pairs of pinnae. The only other taxa of this group within the range of M. millefolia, are M. willardiana and M. russelliana. Mariosousa millefolia is easily distinguished from M. willardiana, which has papery, exfoliating bark and leaves with only 1-3 pinnae pairs. Leaflets with appressed hairs, the stalked rachis glands, and the persistent stipules of M. millefolia separate it from M. russelliana. In addition, M. millefolia is normally a shrub found above 700 m elevation, the other species are trees and commonly occur at lower elevations.

Flowering time

June-August.

Representative specimens

MEXICO:

Sonora:

3 km by road S of Nacozari, 22 Jul 1960, R.S.Felger 3596 (ARIZ, MICH, SD);
El Coyote, jct. of roads to Bacadehuachi, Huachinera, & Guasabas, 23 Jul 1960, R.S.Felger 3619 (ARIZ);
23 km S of Nacozari, alt. 920 m, 26 Oct 1984, R.S.Felger, J.Aronson & A.Shmida 84-382 (ARIZ, TEX);
Swiss Elm Mts., 10 Jul 1907, L.N.Goodding 2319 (GH, MO, UC);
4.2 km S Nacozari, alt. 975 m, 4 Jul 1971, J.R.Hastings 71-195 (ARIZ, SD);
4 miles N of Colonia Oaxaca, alt. 2900 ft., 3 Oct 1965, J.R.Hastings & R.M.Turner 65-25 (ARIZ, SD);
Agua Caliente drainage between Rancho El Alamo and Buena Vista, alt. 950 m, 13 Jun 1992, E.Joyal 2018 (NY, TEX);
5 miles E of Mina Verde, 23 Sep 1934, F.Shreve 6753 (F, MICH, MO);
5.1 miles by road SW of Chinapa, 16 Aug 1958, R.M.Turner & C.H.Lowe, Jr. 2062 (ARIZ);
S of Arispe, ca. 1 km on mesa, 27 Jul 1978, J.Vaughn 661 (MO);
Río Moctezuma, Moctezuma, 27 Jun 1938, S.S.White 339 (GH);
Cañon de Santa Rosa, alt. 4100 ft., 17 Jul 1938, S.S.White 539 (GH, MICH);
Río Bavispe, Colonia Oaxaca, 25 Jul 1938, S.S.White 679 (ARIZ, GH, MICH);
Bavispe, 27-29 Jun 1940, S.S.White 2860 (GH, MICH);
Cañon de Bavispe, 25 Jul 1940, S.S.White 3002 (ARIZ, GH, MICH);
Cañon de Bavispe, 25 Jul 1940, S.S.White 3019 (ARIZ, GH, MICH);
9 miles W of La Angostura, alt. 2900 ft., 19 Aug 1941, S.S.White 4034 (ARIZ, GH, MICH);
Puerto del Molino Quemado, E of Colonia Morelos, alt. 3300 ft., 24 Sep 1940, S.S.White 4511 (ARIZ, GH, MICH);
Colonia Morelos, alt. 2600 ft., 15 Sep-4 Oct 1941, S.S.White 4609 (ARIZ, GH, MICH);
3 miles S of Divisaderos, 30 miles S of Moctezuma, 25 Sep 1934, I.L.Wiggins 7457 (A, ARIZ, F, CH, UC, US);

UNITED STATES:

Arizona:

Cochise Co.:

between Naco and Lowell, alt. 5300 ft., 27 Jul 1966, J.Barrell & S.Spongberg 66-208 (A, US);
foothills E of Douglas, 18 Aug 1937, L.N.Goodding & L.E.Goodding A-9100 (ARIZ);
Bisbee, 27 Jul 1949, W.W.Jones s.n. (RSA);
foothills of the Peloncillo Mts., T22S R32E S32, 9 Jul 1987, V.E.Kluever s.n. (ARIZ);
2.2 miles E of Bisbee city limits on U.S. 80, alt. 5200 ft., 27 Jul 1975, A.Philips, B.Phillips, M.Wiseman, F.Wiseman & D.Ducote 75-56 (ARIZ);
E end of Leslie Canyon, 23 Oct 1978, L.J.Toolin, J.B.Urry & T.R.Van Devender 93 (ARIZ);

Pima Co.:

Box Canyon, Santa Rita Mts., 27 Sep 1966, R.J.Barr 66-199 (ARIZ);
Box Canyon, Santa Rita Mts., 2 Oct 1967, R.J.Barr 67-374 (ARIZ);
Box Canyon, Santa Rita Mts., 2 Jul 1938, alt. 5000 ft., L.Benson 8802 (POM);
Box Canyon, Santa Rita Mts., alt. 4500 ft., 8 Jan 1939, L.Benson 9271 (POM);
Box Canyon, Santa Rita Mts., alt. 5000 ft., 30 Sep 1942, L.Benson 11346 (ARIZ, POM);
Box Canyon, 5.3 miles S of Helvetia, Santa Rita Mts., 2 Jul 1966, alt. 4400 ft., R.L.Bezy 512 (ARIZ);
Box Canyon, 16.5 miles E of Continental, N end of Santa Rita Mts., 21 Aug 1979, J.E.Bowers & S.P.McLaughlin 1870 (ARIZ);
Santa Rita Mts, road from hwy. 83 to Continental, 14 Jul 1940, R.S.Ferris 10054 (UC);
Box Canyon, Santa Rita Mts., summer 1938, alt. 3800 ft., H.S.Gentry 3784 (RSA, UC);
Box Canyon, 16 Oct 1939, L.N.Goodding A-9814 (ARIZ, ASU):
Box Canyon, Santa Rita Mts., 15 Oct 1942, L.N.Goodding 19-42 (ARIZ):
Box Canyon, Santa Rita Mts., 25 Jun 1953, L.N.Goodding 89-53 (ARIZ);
Box Canyon, 15 Sep 1958, L.N.Goodding 491-58 (ARIZ):
Box Canyon, Santa Rita Mts., 23 Aug 1960, L.N.Goodding 251-60 (ARIZ):
base of Rincon Mts., 2 Aug 1931, G.J.Harrison & T.H.Kearney 7978 (ARIZ, F, US);
Box Canyon, E side of Santa Rita Experimental Range S of Tucson, 24 Aug 1948, L.C.Hinckley 4550 (TEX, US);
Box Canyon along Greaterville Road, 5.5 miles E of Madera Canyon Road, alt. 4800 ft., 18 Oct 1989, M.B.Johnson, H.Corbett, S.Luebbemann & P.Rorabaugh 89-153 (ARIZ);
Chimney Creek, Rincon Mts., 6 Oct 1934, T.H.Kearney & R.H.Peebles 10461 (ARIZ, MICH, UC, US);
road between Continental and Greaterville, 6 miles E of Jct. to Madera Canyon, 9 Sep 1976, L.McGill & E.Lehto L20422 (ASU);
Box Canyon, N end of Santa Rita Mts., alt. 4500 ft., 25 Jul 1968, L.McKeighen s.n. (ARIZ, ASU, UC);
7 miles W of hwy. 83 on Greaterville-Madera Canyon Road, alt. 4600 ft., 8 Sep 1973, S.McLaughlin 64 (ARIZ);
1.5 miles NW of Gunsight Pass, alt. 4700 ft., 28 Jun 1986, S.P.McLaughlin & J.E.Bowers 3708 (ARIZ);
vic. of Helvetia, Santa Rita Mts., alt. 4000 ft., 9 Sep 1982, M.Mittleman 373 (ARIZ, ASU);
Rincon Mts., 31 Jul 1932, R.H.Peebles & T.H.Kearney 8745 (ARIZ, F, GH, MICH, POM, US);
Greaterville Road, 5.4 miles W of hwy. 83, 11 Oct 1968, D.Pinkava, D.Keil & E.Lehto 14487 (ASU);
Greaterville Road, 7.8 miles W of hwy. 83, 11 Oct 1968, D.Pinkava, D.Keil & E.Lehto 14492 (ASU, RSA, SD);
Santa Rita Mts., 16 Jul 1884, C.G.Pringle s.n. (CM);
foothills of the Santa Rita Mts., 20 Jul 1884, C.G.Pringle s.n. (A, F, GH, MICH, NY, US);
foothills of the Santa Rita Mts., 9 Sep 1884, C.G.Pringle s.n. (A, F, MO, NY, US);
about 1/2 mile E of the site of Helvetia, alt. 4500 ft., 9 Jul 1983, A.C.Sanders & J.West 3956 (RSA, TEX);
Davidson's Canyon, Santa Rita Mts., 4 Oct 1904, J.J.Thornber s.n. (ARIZ);
Total Wreck Mines, alt. 3500 ft., 10 Jul 1903, J.J.Thornber 107 (MO, POM, UC, US);
Ophir Gulch, 4 miles N and 2 miles W of Sonoita, alt. 4825 ft.,9 Jul 1969, J.P.Tramontano T-25 (ARIZ);
Saguaro National Monument, alt. 4500 ft., 13 Oct 1978, R.M.Turner & L.Gunzel 78-111 (ARIZ, SD);

Santa Cruz Co.:

about 3/4 mile N of Sonoita Creek above Rio Rico, 26 Jul 1981, J.Kaiser 1394 (ARIZ);

New Mexico:

Hidalgo Co.:

extreme SW corner of the county, in Guadalupe Canyon, on and in the vicinity of Hadley Ranch, about 1/2 mile E of Arizona, West edge of Sec. 24 T24S R22W, 17 Aug 1979, R.Spellenberg & R.Repass 5371 (NMC)

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