16. PETALOSTeMON, Michx. PRAIRIE CLOVER.

Calyx 5-toothed. Corolla indistinctly papilionaceous; petals all on thread-shaped claws, 4 of them nearly similar and spreading, borne on the top of the monadelphous and cleft sheath of filaments, alternate with the 5 anthers; the fifth (standard) inserted in the bottom of the calyx, heart-shaped or oblong. Pod membranaceous, enclosed in the calyx, indehiscent, 1--2 seeded.--Chiefly perennial herbs, upright, glandular-dotted, with crowded odd-pinnate leaves, minute stipules, and small flowers in very dense terminal and peduncled heads or spikes.

(Name combined of the two Greek words for petal and stamen, alluding to the peculiar union of these organs in this genus.)

1. P. violaceus, Michx. _Smoothish; leaflets 5, narrowly linear; heads globose-ovate_, or oblong-cylindrical when old; bracts pointed, not longer than the silky-h.o.a.ry calyx; _corolla rose-purple_.--Dry prairies, Minn. to Ind. and Tex., west to the Rocky Mts. July.

2. P. candidus, Michx. _Smooth; leaflets 7--9, lanceolate or linear-oblong; heads oblong_, when old cylindrical; bracts awned, longer than the nearly glabrous calyx; _corolla white_.--With n. 1.

3. P. villsus, Nutt. _Soft-downy or silky_ all over; _leaflets 13--17, linear or oblong_, small (4--5" long); _spikes cylindrical_ (1--5'

long), short-peduncled, soft-villous; _corolla rose-color_.--Wisc. to Mo., west to the Rocky Mts.

4. P. folisus, Gray. _Smooth_, very leafy; _leaflets 15--29, linear-oblong; spikes cylindrical_, short-peduncled; bracts slender-awned from a lanceolate base, exceeding the glabrous calyx; _petals rose-color_.--River-banks, Ill. and Tenn.

5. P. multiflrus, Nutt. _Glabrous_ throughout, erect, branching; leaflets 3--9, linear to oblong; _spikes globose_, the subulate setaceous bracts much shorter than the acutely toothed calyx, petals white.--Kan. to Tex.

17. TEPHRSIA, Pers. h.o.a.rY PEA.

Calyx about equally 5-cleft. Standard roundish, usually silky outside, turned back, scarcely longer than the coherent wings and keel. Stamens monadelphous or diadelphous. Pod linear, flat, several seeded, 2-valved.--h.o.a.ry perennial herbs, with odd-pinnate leaves, and white or purplish racemed flowers. Leaflets mucronate, veiny. (Name from tef???, _ash-colored_ or _h.o.a.ry_.)

1. T. Virginiana, Pers. (GOAT'S RUE. CATGUT.) _Silky-villous_ with whitish hairs when young; _stem erect and simple_ (1--2 high), _leafy_ to the top; leaflets 17--29, linear-oblong; flowers large and numerous, cl.u.s.tered in a terminal _oblong dense raceme or panicle_, yellowish-white marked with purple.--Dry sandy soil. June, July.--Roots long and slender, very tough.

2. T. spicata, Torr. & Gray. _Villous with rusty hairs_; stems branched below, straggling or ascending (2 long), _few-leaved_; leaflets 9--15, obovate or oblong-wedge-shaped, often notched; _flowers few_, in a loose and interrupted _very long-peduncled spike_, reddish.--Dry soil, from Del. and Va. to Fla. and Miss. July.

3. T. hispidula, Pers. Hairy with some long and rusty or only minute and appressed p.u.b.escence; stems slender (9--24' long), divergently branched, straggling; leaflets 5--15, oblong, varying to obovate-wedge-shaped and oblanceolate; _peduncles longer than the leaves, 2--4-flowered_, flowers reddish-purple.--Dry sandy soil, Va. to Fla. and Ala.

18. INDIGFERA, L. INDIGO.

Calyx small, equally 5-cleft. Standard roundish, silky outside, wings coherent; keel erect, gibbous or spurred at base. Stamens diadelphous; connective gland-like. Pod 1--several-seeded, septate within between the seeds.--Herbs or shrubs, mostly canescent with appressed hairs fixed by the middle, with odd-pinnate faintly-nerved leaves, and pink or purplish flowers in naked axillary spikes. (So named because some of the species yield the indigo of commerce.)

1. I. leptosepala, Nutt. A perennial herb, --2 high; leaflets 5--9, oblanceolate; spikes very loose; pods linear, 6--9 seeded, obtusely 4-angled, reflexed, 1' long.--Kan. to Tex. and Fla.

19. ROBiNIA, L. LOCUST-TREE.

Calyx short, 5-toothed, slightly 2-lipped. Standard large and rounded, turned back, scarcely longer than the wings and keel. Stamens diadelphous. Pod linear, flat, several-seeded, margined on the seed-bearing edge, at length 2-valved.--Trees or shrubs, often with p.r.i.c.kly spines for stipules. Leaves odd-pinnate, the ovate or oblong leaflets stipellate. Flowers showy, in hanging axillary racemes. Base of the leaf-stalks covering the buds of the next year. (Named in honor of _John Robin_, herbalist to Henry IV. of France, and his son _Vespasian Robin_, who first cultivated the Locust-tree in Europe.)

1. R. Pseudacacia, L. (COMMON LOCUST or FALSE ACACIA.) Branches naked; _racemes slender, loose_; flowers white, fragrant; pod smooth.--S. Penn.

to Ind., Iowa, and southward. Commonly cultivated as an ornamental tree, and for its valuable timber; naturalized in many places. June.

2. R. viscsa, Vent. (CLAMMY L.) _Branchlets and leaf-stalks clammy; flowers crowded in oblong racemes_, tinged with rose-color, nearly inodorous; pod glandular-hispid.--Va. to N. C. and Ga., in the mountains. Cultivated, like the last, and often escaped. June.

3. R. hispida, L. (BRISTLY L. or ROSE ACACIA.) Shrub 3--8 high; _branchlets and stalks bristly_; flowers large and deep rose-color, inodorous; pods glandular-hispid.--Varies with less bristly or nearly naked branchlets; also with smaller flowers, etc.--Mts. of Va. to N. C.

and Ga. May, June.

20. WISTaRIA, Nutt.

Calyx campanulate, somewhat 2-lipped; upper lip of 2 short teeth, the lower of 3 longer ones. Standard roundish, large, turned back, with 2 callosities at its base; keel scythe-shaped; wings doubly auricled at the base. Stamens diadelphous. Pods elongated, thickish, k.n.o.bby, stipitate, many-seeded, at length 2-valved. Seeds large.--Woody twiners, climbing high, with minute stipules, pinnate leaves of 9--13 ovate-lanceolate leaflets, with or without minute stipels, and dense racemes of large and showy lilac-purple flowers. (Dedicated to the late _Professor Wistar_, of Philadelphia.)

1. W. frutescens, Poir. Downy or smoothish when old; wings of the corolla with one short auricle and an awl-shaped one as long as the claw.--Alluvial grounds, Va. to Fla., west to S. Ind., Kan. and La.

May.--Sometimes cultivated for ornament, as is the still handsomer Chinese species.

21. ASTRaGALUS, Tourn. MILK-VETCH.

Calyx 5-toothed. Corolla usually long and narrow; standard narrow, equalling or exceeding the wings and blunt keel, its sides reflexed or spreading. Stamens diadelphous. Pod several--many-seeded, various, mostly turgid, one or both sutures usually projecting into the cell, either slightly or so as to divide the cavity lengthwise into two.--Chiefly herbs (ours perennials), with odd-pinnate leaves and spiked or racemed flowers. Mature pods are usually necessary for certain identification of the species. (The ancient Greek name of a leguminous plant, as also of the ankle-bone; but the connection between the two is past all guess.)

I. _Pod turgid, completely or imperfectly 2-celled by the intrusion of the dorsal suture, the ventral suture being not at all or less deeply inflexed._--ASTRAGALUS proper.

[*] _Pod plum-shaped, succulent, becoming thick and fleshy, indehiscent, not stipitute, completely 2-celled._

1. A. caryocarpus, Ker. (GROUND PLUM.) Pale and minutely appressed-p.u.b.escent; leaflets narrowly oblong; flowers in a short spike-like raceme; _corolla violet-purple; fruit glabrous, ovate-globular, more or less pointed_, about {2/3}' in diameter, _very thick-walled_, cellular or corky when dry.--Sask. and Minn. to Mo., Col., and Tex. May.

2. A. Mexica.n.u.s, A. DC. Smoother, or p.u.b.escent with looser hairs, larger; leaflets roundish, obovate, or oblong; flowers larger (10--12"

long); calyx softly hairy; _corolla cream-color, bluish only at the tip; fruit globular, very obtuse_ and pointless, 1' or more in diameter; otherwise like the last.--Prairies and open plains, Ill. to Kan., south to Tex. The unripe fruits of both resemble green plums--whence the popular name--and are eaten, raw or cooked, by travellers.

3. A. Plattensis, Nutt. Loosely villous; stipules conspicuous; leaflets oblong, often glabrous above; flowers crowded in a short spike or oblong head, cream-color often tinged or tipped with purple; _fruit ovate, pointed_, and with the calyx _villous_.--Gravelly or sandy banks, Minn.

to Ind. and Ala., west to Col. and Tex.--Var. TENNESSEeNSIS, Gray, has the pod oblong and slightly curved, and much less fleshy. May.

[*][*] _Pod dry, coriaceous, cartilaginous or membranous, dehiscent._

[+] _Pod completely 2-celled, sessile._

4. A. mollissimus, Torr. _Stout, dec.u.mbent, densely silky-villous throughout and tomentose_; leaflets 19--29, ovate-oblong; peduncles elongated; spikes dense, with rather _large violet flowers_ (6--12"

long); pod narrow-oblong (5--9" long), glabrous, somewhat obcompressed and _sulcate at both sutures_, at length incurved.--Neb. to Kan. and Tex., west to Col. The most common "loco"-plant, and said to be very poisonous to cattle.

5. A. Canadensis, L. _Tall and erect_ (1--4 high), _somewhat p.u.b.escent or glabrate_; leaflets 21--27, oblong; _flowers greenish cream-color_, very numerous, in long dense spikes, pods crowded, oblong (6" long), glabrous, _terete, scarcely sulcate_ and only on the back, nearly straight.--River-banks, western N. Y. to N. Ga., and far westward.

6. A. adsurgens, Pall. Ascending or dec.u.mbent (4--18' high), cinereous with minute appressed p.u.b.escence or glabrate; leaflets about 21, narrowly or linear-oblong; spike dense, with medium-sized pale or purplish flowers; _p.u.b.escence of calyx appressed_; pod oblong (4--5"

long), _finely p.u.b.escent, triangular-compressed, with a deep dorsal furrow, straight_.--Red River valley, Minn., to W. Kan., and westward.

(Asia.)

7. A. hypoglottis, L. _Slender_ (6'--2 long), diffusely proc.u.mbent or ascending, _with a rather loose p.u.b.escence_ or nearly glabrous; leaflets 15--21, oblong, obtuse or retuse; _flowers violet, capitate; calyx loosely p.u.b.escent; pod_ as in the last, but _ovate_ and _silky-villous_.--Red River valley, Minn., to central Kan. and westward.

[+][+] _Pod not completely 2-celled._

[++] _Pod stipitate, pendent._

8. A. alpnus, L. _Diffuse_ (6--12' high), smooth or slightly hairy; leaflets 13--25; flowers _violet-purple_, or at least the keel tipped with violet or blue; calyx campanulate; pod narrowly oblong, short-ac.u.minate, _black-p.u.b.escent_, triangular-turgid, deeply grooved on the back, straight or curved, its stipe usually rather exceeding the calyx.--Rocky banks, Lab. to Maine and N. Vt.

9. A. Robbinsii, Gray. Nearly smooth and _erect_ (1 high), slender; leaflets 7--11; calyx more oblong; _flowers white_; pod oblong (6"

long), obtuse or acutish, _minutely darkish-p.u.b.escent_, somewhat laterally compressed, _not dorsally sulcate_ or obsoletely so, straight or somewhat incurved, rather abruptly narrowed at base into the often included stipe.--Rocky ledges, Vt.

10. A. racemsus, Pursh. Stout (1--2 high), erect or ascending, appressed-p.u.b.escent or glabrate; leaflets 13--25; flowers numerous, white, pendent; calyx campanulate, gibbous, white-p.u.b.escent; pod straight, narrow, 1' long, acute at both ends, triangular-compressed, deeply grooved on the back, the ventral edge acute.--Neb. to Mo., and westward.

[++][++] _Pod sessile._