Astragalus Pulsiferae

Delicate, diffuse, caulescent perennial, the stems arising together from the subterranean (or sometimes superficial) crown of a woody taproot, gray-villous or -villosulous nearly throughout with fine, spreading or loosely ascending, straight or sinuous hairs up to 0.5—1.6 mm. long; stems few or several, decumbent or prostrate, (0.4) 1—2.5 (3) dm. long, subterranean, naked and glabrous for a space of (0) 2-8 cm., divaricately branched on emergence and the more vigorous branches again branched or spurred, floriferous upward from well below the middle, the peduncles sometimes paired with a branchlet at some distal axils; stipules triangular or triangular-acuminate, 1-4.5 (5) mm. long, the lowest papery-scarious, the upper thinly herbaceous, all rather strongly adnate to the petiole-base and decurrent around ? to the whole stem’s circumference, either all free, or more commonly a few of the lowest connate into a cuplike sheath; leaves 1-4.5 (5.5) cm. long, with slender or subfiliform, usually short petioles and (3) 7-13 commonly crowded, oblanceolate- or obovate-cuneate, retuse or more rarely truncate and apiculate, loosely folded leaflets 2—12 mm. long; peduncles very slender, incurved-ascending, 0.4-2.5 cm. long; racemes shortly but loosely (2) 3-13-flowered, the flowers delcined in age, the axis not or scarcely elongating, (2) 4-12 mm. long in fruit, commonly produced as a subulate appendage beyond the last flower; bracts submembranous, triangular to linear-lanceolate, 0.8-2.4 mm. long; pedicels filiform, at anthesis 0.7-1.4 (1.6) mm., in fruit 1-1.8 mm. long; bracteoles 0; calyx 3.2-5.8 (6.2) mm. long, white-villous or -villosulous, the subsymmetric disc 0.4—0.8 mm. deep, the shallowly campanulate tube 1.3-2.6 mm. long, 1.6—2.2 mm. in diameter, the linear-lanceolate or setaceous teeth 1.4—3.6 mm. long, the whole becoming scarious, ruptured, marcescent; petals whitish, the banner veined, and the keel tipped with lilac (often drying yellowish); banner recurved abruptly through 90-100°, ovate-cuneate, notched at apex, (5.2) 6-8.5 mm. long, 4-5.6 mm. wide; wings (either a trifle longer or shorter than the banner) 5.4-7.2 mm. long, the claws 1.6-2.2 mm., the oblanceolate or obliquely triangular-elliptic, obtuse blades 4—5.5 mm. long, 1.5—2.3 mm. wide, both incurved but the left one more abruptly so and its inner edge infolded; keel 3.4-5.3 mm. long, the claws 1.5-2.2 mm., the half-circular blades 2.1-3.4 mm. long, 1.3-2.1 mm. wide, abruptly incurved through 100—130° to the bluntly triangular, obscurely porrect apex; anthers 0.3—0.45 (0.5) mm. long; pod widely spreading or declined (often humistrate), sessile on the obconic receptacle, very obliquely half-ovoid or ovoid-ellipsoid, bladdery-inflated, (0.8) 1-2 cm. long, (5) 6-11 (or when pressed seemingly up to 13) mm. in diameter, at base broadly obconic or contracted into a narrowly turbinate neck, more gradually tapering distally into a broadly triangular or triangular-acuminate, laterally compressed beak, sulcate ventrally at the middle and dorsally toward the base, the filiform ventral suture straight or concavely arched, the dorsal suture gibbous-convex, the papery-membranous, subdiaphanous, pale green or minutely purple-dotted, thinly long-villous or villosulous valves becoming stramineous and delicately reticulate, not inflexed or very narrowly so toward the pod’s base as a vestigial septum less than 0.2 mm. wide; ovules (3) 5-9; seeds brown or brown speckled with purple, smooth but dull, 1.9-3.2 mm. long.

In a foreword to the section I have described the Ames milk-vetch, A. Pulsiferae, as enigmatically variable, alluding not alone to the differences in position of the root-crown and in connation of the lower stipules observed in otherwise similar plants, but also to a racial situation in the species set against a curious geographic background. The nomenclaturally typical phase of A. Pulsiferae is distinguished by its vesture of exceptionally long, horizontally spreading hairs, stems freely branching into fan-shaped sprays, a calyx with attenuately drawn- out teeth, and at least one or two pairs of stipules connate into a papery cup at the lowest subterranean nodes of the stem. It is confined to a small area along the east piedmont of the northern Sierra Nevada and plains adjoining and, so far as known to me in the field, is found in loose sandy soil or in depressions of valley dunes. Occasional populations found in the same area, at least sometimes in stiffer soils, combine the characteristic vesture and calyx with a superficial root-crown and stipules all free to the base; samples from these, judged in isolation from the whole species, cannot be excluded on technical grounds from sect. Inflati. I have fancied at times that A. Pulsiferae might be better associated with A. (Ervoidei) microcystis, although the presence of a septum in some forms must be weighed against a similarity (perhaps altogether fortuitous and superficial) in the growth-habit, form of the flower, and few ovules. Further complicating the picture there exists also in northern California, close to var. Pulsiferae but slightly to the north and west, a nearly related form, var. Suksdorfii, which differs in its comparatively short pubescence of more sinuous hairs, and shorter calyx-teeth, while the simpler stems arise from a root-crown situated only rarely and at best shallowly below the level of the soil. The known range of var. Suksdorfii is dramatically bicentric, documented by several collections from Plumas, Lassen, and Siskiyou Counties, California, and by three, taken at the same place at intervals between 1883 and 1908, from the southern foothills of Mount Adams in the Cascade Range of Washington. This disjunct (or even if some gaps are filled in by further collecting, far-flung) dispersal suggests that var. Suksdorfii has a longer history than can be claimed for var. Pulsiferae; it seems likely that the latter is the more specialized and derived form. If the cryptophytic growth-habit can also be shown to be derived, and with it the union of the lower stipules, the affinities and systematic position of the species will need reappraisal.