Astragalus crassicarpus

Of medium or robust stature, with a woody taproot (up to 5 cm. in diameter just below the crown, but usually much less) and several decumbent, ascending, or sometimes suberect stems arising from a determinate root-crown or (in one var.) from slender, subterranean caudex-branches, the herbage variably pubescent, green or cinereous, the leaflets glabrous or medially glabrescent above; stems (0.5) 1-6 dm. long, simple or bearing a few spurs or branchlets near the base, the main axis commonly elongating beyond the last peduncle, the flowering racemes situated above the middle but the fruiting ones at or below the middle of the stems; stipules submembranous, pale green, pallid, or purplish, sometimes several- nerved, 3-10 mm. long, the lower ones (sometimes all) ovate or ovate-acuminate, the upper commonly triangular- or lance-acuminate or -caudate, decurrent around ± ½ the stem’s circumference, glabrous dorsally, ciliate, the margins nearly always beset with a few peg- or tack-shaped processes mixed with or even replacing the hairs; leaves (2) 3.5-15 cm. long, the upper ones shortly petioled or subsessile, with (11) 15-33 broadly oval to linear-elliptic, obtuse or acute, or (in some lower leaves) truncate-emarginate, mostly flat leaflets 3-24 mm. long; peduncles (0.5) 2-14.5 cm. long, equaling or commonly shorter than the leaf; racemes shortly (5) 7-25 (30), more rarely 20-35-flowered, rather dense at early anthesis, the axis usually somewhat elongating, 1-7.5 cm. long in fruit; bracts membranous, pallid or purplish, lance-acuminate or linear-lanceolate, 2.5-7.5 mm. long, often reflexed in age; pedicels ascending or a little arched outward, at anthesis slender, 1-2.7 mm. long, in fruit thickened, often clavate, (2) 2.7-7.5 mm. long; bracteoles usually present, inserted at base of the calyx or up to 2.5 mm. below it, often conspicuous, rarely rudimentary or 0; calyx (6.6) 7.7-13.8 mm. long, the oblique disc (0.8) 1-2.2 mm. deep, the broadly or deeply campanulate, cylindro-campanulate, or rarely cylindric tube (5.2) 5.6-9.7 mm. long, the subulate or triangular-subulate teeth (1.3) 1.7-4.8 mm. long, the ventral pair mostly broadest but either longest or shortest, the whole early becoming scarious, irregularly circumscissile, leaving the pod naked; petals purple, lilac, cream-colored, or greenish-white, the keel in any case purple- or pink-tipped; banner obovate-cuneate, broadly oblanceolate, rhombic-oblanceolate, or -elliptic, notched, (16) 16.5-25 (27) mm. long; wings shorter, the blades linear-oblong, lance-oblong, or narrowly elliptic-oblanceolate, obtuse or sometimes obliquely emarginate, straight or a trifle incurved in the distal half; keel (10.7) 12-20.7 mm. long, the blades half-obovate or lunately elliptic, rather abruptly incurved through (80) 85-95° to the blunt apex; anthers (0.55) 0.6-0.9 mm. long; pod spreading or ascending (humistrate except sometimes in var. trichocalyx), sessile, globose, broadly and plumply oblong-ellipsoid, -ovoid, or -obovoid, 1.5-4 cm. long, 7/8—1½ times longer than wide, abruptly obtuse or truncate at both ends, or a trifle retuse or umbilicate at apex and there abruptly contracted into a conic-subulate, cusplike beak 1—3 mm. long, the body a little obcompressed, shallowly sulcate or merely depressed along the sutures, the fleshy, glabrous, green but often red-cheeked valves at first firm and succulent (and if dried at this stage collapsing inward and becoming irregularly and coarsely wrinkled, leaving the sutures salient), composed of 3 layers: a thin outer coat and a similar inner one of small cells, these becoming leathery, the outer one eventually brown or blackish and nearly smooth, and a much thicker intervening layer of large cells filled with a sweet juice, this ultimately drying out to a pale, alveolate- spongy or pithy texture, the whole valve-wall 1.2—5 mm. thick (at least near the sutures), the endocarp inflexed across the pulpy-filamentous cavity as a papery septum 8—15 mm. wide, this produced through the valve-wall to unite with or at least to meet the immersed ventral suture; dehiscence very tardy, either occurring on the ground by gradual weathering and decay over winter, the exocarp then sometimes separating as a papery shell, the beak splitting but not gaping to release the seeds, or the whole pod splitting through both sutures and the septum and separating into two false carpels; ovules 34—77; seeds soot-black, smooth or sparsely pitted, dull, (1.9) 2.1-4.4 mm. long.

The varieties of A. crassicarpus, all of which (except the newly described var. cavus) have been accepted at one time or another as distinct species, differ considerably in degree of distinctness. Thus var. crassicarpus and var. Paysoni are separable only by tenuous differential characters, often difficult to apply to herbarium specimens, and they might be united without any great loss; whereas var. trichocalyx, which differs (at least ideally) from var. crassicarpus in growth-habit, pubescence, and especially in ecology, might with reason be retained at the specific level. The var. Berlandieri, characterized by a branching caudex below ground, is another striking type in its extreme form. However when allowance has been made for a latitude of variation in the pods no greater than that found in the majority of widely dispersed astragali, the fruit can be considered essentially homogeneous throughout the species, differing from one variety to the next in average but not in absolute size and in the average width of the pod walls.

The status of the name A. crassicarpus is somewhat controversial, being vulnerable to criticism from two directions. The Fraser Brothers’ Catalogue has been attacked and defended in recent years (cf. Shinners, Cronquist & al. in Rhodora 57: 290; 58: 23, 281; 59: 100. 1955— 1957) as a valid medium of publication, neither side to the question having gained a conclusive victory. A graver fault is the extreme brevity of the original description and the fact that Nuttall himself adopted Pursh’s A. carnosus in place of his own (or what is presumed to be his own) proposition. However no reasonable doubt has ever been entertained as to the identity of A. crassicarpus, which was already known to botanists contemporary with Nuttall. If Nuttall’s name should finally prove unacceptable to the majority, the species must assume the epithet caryocarpus Ker (cf. further under var. crassicarpus).

The ground-plum, buffalo-plum, or pomme de prairie is one of the very few American Astragali which has acquired a name truly current in the vernacular of the country, due to its value as food. The raw fruit is succulent and sweet but hardly appetizing, although it is said to become more palatable (T. E. Wilcox, Fort Niobrara in 1888, NY) after cooking, the boiled pods supposedly tasting like string beans. The fruits are gathered by prairie dogs for their winter store and are attractive to other rodents when ripe and dry. I once found, in a corner of a neglected closet, a hoard of some fifty pods of A. crassicarpus and A. gypsodes which had been pilfered from the herbarium by mice and partly devoured. In this respect the pods of the Sarcocarpi resemble those of A. longiflorus Pall. and probably other members of the appropriately named Old World sect. Myobroma Bge.