Monographs Details: Astragalus rattanii A.Gray var. rattanii
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:

329a. Astragalus Rattani var. Rattani

Hairs of the herbage mostly up to 0.3-0.45 mm. long; leaflets (5) 7-11 (13); racemes 2-10-flowered; calyx-tube 2.7-3.4 mm. long, 1.8-2.6 mm. in diameter, the disc 0.7-1 mm. deep, the teeth 0.9-1.7 mm. long; petals pink-purple with paler claws and wings-tips, rarely white; banner 4.9—6.4 mm. wide; wings (7.7) 8-10.4 mm. long, the claws (2.5) 2.7-3.7 mm., the blades 5.9-7.6 mm. long, 1.9—3 mm. wide; keel-claws 2.4—3.6 mm., the blades 4.5—5.5 mm. long, 2—2.4 mm. wide.—Collections: 20 (i): representative: Peirson 7058 (NY, RSA); M. S. Baker 9535 (CAS); Eastwood 12,944, 12,944a (CAS); Barneby 11,573 (CAS, NY, RSA); Jepson 13,756 (UC-JEPS).

Open grassy hillsides, gravelly flats in the valleys, and gravel bars of stream and river beds, 100-2000 (2500) feet, uncommon but forming colonies in the outer North Coast Range of California, especially in the valleys of the Mad, Van Duzen, and Eel Rivers, central Humboldt to central Mendocino and extreme northwestern Lake Counties, east to the east slope of the Yollo Bolly Range in western Tehama County.—Map No. 148.—Mid-April to July.

Astragalus Rattani (Volney Rattan, 1840-1915) Gray in Proc. Amer. Acad. 19: 75. 1883.—"Mendocino Co., California, on prairies north of Mad River, and on Rattlesnake Creek, June, 1882, V. Rattan."—Holotypus, GH! isotypi (ex herb. Gray.), K, ND, P!—Hamosa Rattani (Gray) Rydb. in Bull. Torr. Club 54: 324. 1927.

The typical form of the Rattan milk-vetch is notable for the great length and slender outline of the fruits. They are commonly almost straight and ascend, two or three together, from the tips of the peduncles in a manner reminiscent of Amsonia follicles or the long-beaked mericarps of the umbellifer Scandix. In their length they seem to represent an evolutionary peak among the cismontane annuals and are probably more highly modified than the pods of var. Jepsonianus, which is both geographically and morphologically more nearly central to its group. The flowers of var. Rattani are pink-purple throughout, but the color varies in vividness, and albino individuals are known to occur. A specimen from Dos Rios, Mendocino County (E. W. Wright in 1927, CAS) was identified by the collector as a locoweed, but the species should not be condemned without experimental proof.