Astragalus Wootoni

Low but often coarse and leafy, winter-annual or biennial, thinly or when young rather densely strigulose, villosulous, or pilosulous with fine, straight and appressed, narrowly to widely ascending, or incurved-ascending and spreading hairs up to 0.4-0.8 mm. long, the herbage pale green, yellowish-green, or greenish- cinereous, the leaflets glabrous or medially glabrescent above; stems sometimes solitary and erect in seedling but already flowering plants, commonly several or numerous from the freely forking, ultimately indurated base, decumbent and incurved-ascending or almost prostrate, (0.35) 0.7-3 (5) dm. long, branched or spurred at most or all nodes preceding the first peduncle, pale green or purplish becoming stramineous; stipules submembranous becoming papery, triangular or triangular-acuminate, (1.5) 2.5-7 (10) mm. long, decurrent around half or the lowest more than half the stem’s circumference, the latter with contrapetiolar margins sometimes contiguous but free, rarely very shortly and obscurely connate (less so than adnate); leaves (2) 4-10 (12) cm. long, all shortly petioled or the uppermost subsessile, with (7) 11-23 narrowly oblanceolate, linear-oblong, or oblong- obovate, retuse-truncate or obtuse, often callous-mucronulate, folded or rarely flat leaflets 5-20 mm. long; peduncles incurved-ascending, (0.5) 1.5-5.5 (7) cm. long, shorter than the leaf; racemes loosely 2-10 (15)-flowered, the flowers ascending at first anthesis, spreading or declined thereafter, the axis little elongating, (0.5) 1-4 (5) cm. long in fruit; bracts submembranous, ovate or lanceolate, 1-3.2 mm. long; pedicels at anthesis slender, ascending, straight or nearly so, 1-2 mm. long, in fruit arched, a trifle thickened, 1.5-3.5 mm. long, persistent; bracteoles nearly always 2; calyx 4.3-6.4 mm. long, strigulose or villosulous with white or sometimes largely black hairs, the subsymmetric disc 0.5-1.1 mm. deep, the campanulate or turbinate-campanulate tube 2.1-2.9 (3.2) mm. long, 1.8-2.3 mm. in diameter, the lance-subulate teeth 2—3.5 mm. long, the whole becoming papery, ruptured, marcescent; petals whitish, sometimes tinged with pink or lavender, or pale to vivid reddish-lilac; banner recurved through ± 45°, ovate- or obovate-cuneate or flabellate, 4.6—7.5 mm. long, (3.2) 3.5—6 mm. wide; wings a trifle shorter or rarely a trifle longer than the banner, (4.1) 4.9-7.5 mm. long, the claws (1.4) 1.6-2.6 mm., the oblong or oblong-obovate, obtuse, sometimes erose-undulate blades (2.9) 3.5—5.6 mm. long, 1.2—2.2 mm. wide, both incurved but the left one further and more abruptly so; keel either a trifle shorter or longer than the wings, banner, or both, (4.1) 4.4—6.4 mm. long, the claws 1.5—2.6 mm., the half-obovate or -circular blades 2.7—4.3 mm. long, 1.5—2.4 mm. wide, incurved through 90-100° to the broad and blunt, more rarely triangular and subacute, sometimes obscurely porrect apex; anthers (0.25) 0.35-0.5 (0.6) mm. long; pod loosely spreading or declined, commonly humistrate (and then often apparently ascending), sessile on the conical receptacle and readily disjointing, broadly and subsymmetrically, or sometimes somewhat obliquely ovoid, ovoid-ellipsoid, ellipsoid, or subglobose, bladdery-inflated, (1) 1.5-3.7 (4.3) cm. long, (0.8) 1.2-2 (or when pressed apparently to 2.4) cm. in diameter, broadly cuneate or rounded at base, contracted just below the apex into a short and obscurely differentiated, deltoid, laterally flattened beak, otherwise subterete or openly and shallowly silicate along one or both sutures, the sutures filiform, subequally convex or the dorsal one more strongly so, the thin, green or purplish-tinged, very rarely lightly mottled, thinly strigulose, subvillosulous, or glabrate valves becoming papery, stramineous, lustrous, delicately reticulate, not inflexed, the funicular flange none or up to 0.7 (1) mm. wide; dehiscence apical, after falling; ovules (10) 13-21; seeds brown, orange- or purplish-brown, sometimes purple-speckled, roughened, and often sparsely pitted, dull, (2) 2.3-3 mm. long.

With the exception of the more northern A. Geyeri, the Wooton milk-vetch is the most widely dispersed member of its section and is perplexingly variable, most probably composed of several or even many, small geographic races adapted to particular sets of environmental circumstances. My picture of A. Wootoni has been pieced together over a period of years. Looking back I suspect that if all the material that has passed through my hands could be reassembled in one place, a more refined perception of the racial structure of the species might be possible. This being at present impracticable, I must limit myself to a brief discussion of the types of variation encountered in the complex.

In the first place the average plant of A. Wootoni, although potentially biennial, behaves as an annual during the first season of growth, ordinarily coming into flower within two months of the seed’s germination and fruiting soon after. As always with desert annuals, the Wooton milk-vetch varies enormously in stature and luxuriance from year to year according to the amount and timing of the spring rains or thaws. In New Mexico’s summer rainfall belt one may find late in the year a colony of old, basally indurated plants intermingled with a new crop of seedlings; and together they exhibit almost the gamut of size-variation known in the whole species. Elsewhere occur colonies of juvenile plants with no sign of a generation dating back to the preceding spring or season, and it is probable that some populations or strains of A. Wootoni are obligately monocarpic.

In the United States and northern Mexico the vesture of A. Wootoni is ordinarily sparse, appressed or nearly so; in trans-Pecos Texas, and sporadically in southern New Mexico, the hairs become somewhat looser or incurved; and from San Luis Potosi south into Puebla, the herbage is loosely pilosulous with incurved-ascending and spreading hairs. Transition from one extreme type of indumentum to the other is very gradual and does not of itself provide a basis for varietal segregation. On the higher plains of northern Arizona and New Mexico, the petals are whitish or sometimes faintly roseate, but southward pink- or reddish-lilac flowers become increasingly common, especially on the low sandy deserts along the Rio Grande and in the sahuaro forests of southern Arizona, without anywhere wholly replacing the whitish form. The normal vigorous raceme in northern Mexico and United States is about 5-10-flowered, although counts of 3 up to 15 are on record; southward the flowers are only 2-5. The leaflets of A. Wootoni are ordinarily quite narrow, or appear so due to folding of a relatively broad, oblong type, but here and there more amply leafy colonies or individuals have been noticed.

The pod of A. Wootoni fluctuates in size between extremes of 1 and 4.3 cm. in length and between 8 and 20 mm. in diameter, but the normal range is smaller, ± 1.5-3.5 × 1-1.7 cm. In general a short pod tends to be plumply ovoid or subglobose; but as increasing length does not go hand in hand with proportionately greater width or inflation, the longest pod assumes a more narrowly elliptic profile. A small pod is commonly encountered on starveling individual plants, but may occur in the most vigorous and amply leafy states, where its size must be governed genetically. Since it is impossible, however, to distinguish in practice between the small-fruiting individual from a small-fruting member of a uniform population, I cannot maintain Phaca Tracyi which represents a type common in the Big Bend country of western Texas and may be a little more substantial than a casual minor variant. A pod of subsymmetric outline, with sutures almost equally convex, and terminating in an exceptionally short and broad, commonly erect and often obscurely differentiated beak, is the hallmark of A. Wootoni, as I conceive the species. Nevertheless it is an easy matter to pick out from any substantial folder of specimens a series of fruits progressively more oblique and more prominently and obliquely beaked until a stage indistinguishable from the pod of A. allochrous is reached. Apparent intergradation between A. Wootoni and its close relative A. allochrous, usually distinguished by its raceme of some 10-20, slightly larger flowers, is discussed under the latter heading.

The Wooton milk-vetch is a pest of rangelands in western Texas and southern New Mexico and Arizona, where it is reported (Kearney & Peebles, 1951, p. 463) as toxic to horses, cattle, and sheep. Both A. Wootoni and A. allochrous are known to Spanish-speaking shepherds and cowboys as garbanzillo, a term originally applied in Spain to A. lusitanicus Lamk. and in South America to A. Garbancillo Cav. and related forms. In the New World the term (diminutive of chick-pea) has taken on a generic connotation, being applied widely and indiscriminately by Latin Americans to any astragalus with bladdery fruits.