Astragalus lentiginosus var. borreganus M.E.Jones
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Authors
Rupert C. Barneby
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Authority
Barneby, Rupert C. 1964. Atlas of North American Astragalus. Mem. New York Bot. Gard. 13(2): 597-1188.
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Family
Fabaceae
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Scientific Name
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Type
“Collected at Borregos Springs, Southeastern California, by Orcutt."—Holotypus, collected by T. S. Brandegee, not by Orcutt, April 16, 1895, UC! isotypus (fragm.), POM!
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Synonyms
Astragalus coulteri Benth., Tragacantha coulteri (Benth.) Kuntze, Astragalus lentiginosus var. coulteri (Benth.) M.E.Jones, Cystium coulteri (Benth.) Rydb., Astragalus arthu-schottii A.Gray, Astragalus agninus Jeps., Cystium agninum (Jeps.) Rydb.
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Description
Variety Description - Commonly winter-annuals with a single stem either simple or branched from near the base, but sometimes persisting into a second year and then forming bushy clumps of several or even many stems erect and ascending from an indurated root, densely pubescent throughout with short, subappressed and some longer, narrowly ascending, straight or partly sinuous hairs up to 0.55—0.9 (1.2) mm. long, silvery- silky throughout or the leaves sometimes greenish-gray in age; stems stout or quite slender, flexuous, 1—3 dm. long; leaves 6—10 (16) cm. long, with (7) 15-19 broadly obovate-cuneate to elliptic-oblanceolate, obtuse or emarginate to retuse, flat or loosely folded leaflets 4-14 (21) mm. long; peduncles stiffly erect or somewhat incurved, 5—10 cm. long; racemes loosely, sometimes remotely 13—35 (48)- flowered, the axis early elongating, (4.5) 6—18 (26) cm. long in fruit; calyx 5.2-6.6 mm. long, densely strigulose-villosulous with white and often some fuscous or black hairs, the tube 4-5.1 mm. long, 2.5-3.5 mm. in diameter, the subulate or triangular teeth 1-2.3 mm. long; petals pink-purple; banner ovate-cuneate, broadly notched, 12—14.8 mm. long, 7—9.4 mm. wide; wings 11.3—14.4 mm., the claws (3.9) 4.3-5.5 mm., the blades 7.4-9.3 mm. long; keel 10.4-12.5 mm. long, the claws 4.3—5.7 mm., the blades 6—7.3 mm. long, 2.7—3.7 mm. wide; pod erect or incurved-ascending at a narrow angle, lanceolate or narrowly ovate-acuminate in profile, gently incurved, 1.5—2.3 cm. long, 4.5—6 mm. in diameter, slightly turgid but not or scarcely inflated, the sub terete body shallowly sulcate along both sutures, passing gradually into the shortly triangular, cuspidate beak, the thin, greenish- stramineous or faintly mottled valves commonly concealed by a dense coat of silky, strigulose-villosulous hairs, becoming papery, finely reticulate, inflexed as a complete or nearly complete septum; ovules (10) 13—20.
Distribution and Ecology - Sandy flats and semistabilized dunes, with Larrea, locally abundant after rains but scarce or absent in dry seasons, from 100 feet below to 800 feet above sea level, southern Colorado Desert, California, in eastern San Diego and Imperial Counties, east into the Yuma Desert in extreme southwestern Arizona and adjoining northwestern Sonora (presumably also northeastern Baja California), apparently disjunctly at 900-2500 (3000) feet in the Mohave Desert, from near Baker and Kelso to Ivanpah Valley, eastern San Bernardino County, California.— Map No. 132—Late February to May.
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Discussion
The varieties of freckled milk-vetch described up to this point have in common a pod either consistently inflated and bladdery or so often so that one little-swollen can be overlooked in practice as a rare minor variant. With var. borreganus I begin to take up those in which the pod is characteristically uninflated and varies from lanceolate to linear-oblong or fusiform in profile. Although these forms are here arranged side by side at the end of the species, as though a narrow pod signified a close interrelationship, it is likely that they arose separately by parallel mutations from different sources in the A. lentiginosus complex. The var. borreganus is almost certainly derived from a common precursor with var. coachellae and var. variabilis. Although very distinct upon first sight, because of the long, open racemes of narrow, white-silky pods, it is very close to var. coachellae. I have mentioned elsewhere and illustrated (1945, p. 132, Pl. IV, fig. 20) a collection from Imperial County, unquestionably of this entity, which bears a moderately swollen pod and can scarcely be separated from the silky-pubescent phase of var. variabilis found on the central Mohave Desert. It is generally true of var. borreganus that it differs from var. coachellae in having a root more often annual and a raceme averaging longer and looser; while the ovules are decidedly fewer, and the flower, although of nearly the same length, is somewhat differently proportioned, with a calyx shorter and keel longer in relation to the banner. In fine detail the flower is more nearly that of var. variabilis, and it is hardly surprising that Gray, who had seen pods of neither, associated the first collections of the two varieties in his description of A. Arthu-Schottii.
Unless it is by accident that we have no evidence of its presence in stations intermediate between the two foci of abundance in the eastern Mohave and southern Colorado Deserts, the Borrego milk-vetch has an unusual, decidedly bicentric pattern of dispersal. Possibly two races are involved; if so, it would be no surprise to learn that these arose separately, the eastern one, composed of plants normally coarser than the southern one, from var. variabilis and the other from var. coachellae. Further field observation and reappraisal of the herbarium record may throw light on this speculation.
For discussion of the synonym A. Coulteri, see under var. coachellae.
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Objects
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Distribution
California United States of America North America| Arizona United States of America North America| Sonora Mexico North America|