Monographs Details: Astragalus rattanii var. jepsonianus Barneby
Authors:Rupert C. Barneby
Authority: Barneby, Rupert C. 1964. Atlas of North American Astragalus. Mem. New York Bot. Gard. 13(2): 597-1188.
Family:Fabaceae
Discussion:

329b. Astragalus Rattani var. Jepsonianus

A little more thinly pubescent than var. Rattani, the hairs a trifle shorter, up to 0.2-0.4 mm. long; leaflets mostly 7 or 9, cuneate-oblanceolate; racemes 4-9-flowered; calyx-tube 1.8-2.4 mm. long, 1.3-1.8 mm. in diameter, the disc 0.5-0.7 mm. deep, the teeth 0.6-1.2 mm. long; petals commonly bicolored, only the distal third of the banner and the keel-tip purple-maculate, but sometimes all suffused with pink-purple, exceptionally all white; banner 3.5—5 (5.4) mm. wide; wings 5.8-8 mm. long, the claws 1.7-2.3 mm., the blades 4.7-6.5 mm. long, 1.5—2.4 mm. wide; keel-claws 1.4—2.3 mm., the blades 2.5—3.5 mm. long, 1.5-1.8 mm. wide.—Collections: 16 (o); representative: Eastwood & Howell 5634 (CAS); Ferris 706, 6281 (DS, NY); M. S. Baker 8938, 12,940 (CAS); Mrs. Bruce 2078, 2432 (DS, NY).

Meadows, grassy hillsides and valley floors, and openings in chaparral, commonly on or near serpentine outcrops, about 1100-1900 feet, local but forming colonies, inner North Coast Range of California, southern Lake and northern Napa to western Colusa and western Tehama Counties, northeast (in unknown habitats) to the floor of the Sacramento Valley in Yolo and Butte Counties.— Map No. 148.—April to early June.

Astragalus Rattani var. Jepsonianus (Willis Linn Jepson, 1867-1946, most distinguished botanist of his generation in California) Barneby in Aliso 4: 137. 1958.—"California. Walter Springs, Napa County, April 30, 1939, J. T. Howell No. 14,625 ... "—Holotypus, CAS! isotypus, DS!

The existence of a short-fruiting form of the Rattan milk-vetch, apparently replacing the typical form of its species in the inner North Coast Range, was first mentioned by Jepson (1936, p. 379), who cited collections from western Colusa and Tehama Counties as examples. Plants characterized by a fruit about 1.5-3 cm. long occupy a natural area extending from the serpentine country in southern Lake and adjoining Napa County north and east to the floor of the Sacramento Valley in Butte and Yolo Counties; and the short pod coincides with relatively few ovules and slightly but consistently smaller flowers. In Butte County (from which there are three collections, but only one sufficiently documented to permit mapping) the variety overlaps the range of A. pauperculus, which is easily distinguished by its elongating raceme-axis and mottled, commonly resupinate, shorter and slightly broader (thus proportionately a good deal broader) pod. In Lake and Napa Counties var. Jepsonianus is sympatric with A. Breweri and closely approaches A. Clarianus, the differential characters of which are stressed elsewhere.

Like all the cismontane annuals, A. Rattani var. Jepsonianus is a pretty little plant, with three or four pairs of small, neatly cuneate-oblanceolate leaflets to the average leaf, subumbel- late inflorescence of about seven flowers, and an extremely slender, usually incurved pod dorsally grooved when young but often subterete when distended by the crowded, quadrately oblong seeds. The flowers vary considerably in color, being sometimes uniformly pink-purple as in var. Rattani, perhaps more often bicolored with the pigment concentrated in the form of a broad margin or transverse band across the distal third of the banner and the keel-tip, the remainder being white or faintly roseate.

Although described only latterly in its present status, the substance of var. Jepsonianus has been recognized as a species distinct from A. Rattani under the name A. (or Hamosa) Clarianus by Abrams and by Rydberg, a point mentioned further under the next. The finely executed figure of "A. Clarianus" in Abrams (1944, fig. 2895) portrays var. Jepsonianus to the life.