7. ARABIS, L. Rock Cress. (Name from Arabia, the native country of some of the species.) Sepals mostly erect; silique linear compressed; valves each with one or three longitudinal veins, seeds in a single row in each cell, mostly margined, cotyledons accumbent or loblique. - Fls. white.

* Leaves (all or at least the radical) pinnatifid......................................

Nos. 1, 2.

* Leaves all undivided, toothed or entire, often clasping. (a)

a Siliques short (6 - 12") and straight. Seeds not winged..................................

Nos. 3, 4.

a Siliques longer (1 - 2'), straight or curved. Seeds not winged,............................

Nos. 5, 6.

a Siliques long (3'), curved, pendant. Seeds winged.........................................

Nos. 7, 8.

1 A. Ludoviciana Meyer. All the lvs. pinnatifid or pinnate, smoothish; st branched at base; siliques and pedicels ascending; sds. bordered.-Crucifeeae Crucifers Part 4 254 N. Car. and Ky. (Curtis) to (Macon) Ga. Sts. 6 - 10' high, slender. Leaves 1-2' long, at first rosulate, of 6 - 9 pairs of oblong, few-toothed leaflets, rachis slightly winged. Pods 7 - 10" by 1", valves veiny. Fls. minute, white. Mar., Apr.

2 A. lyrata L. Upper lvs. smooth, linear, entire; radical lvs. lyrately pinnatifid, often pilous; st. branched at base; pedicels spreading; siliques erect, seeds not bordered.-Crucifeeae Crucifers Part 4 255 On rocky hills, Can. and Wis. to Va. Sts. declined at base, 6 - 12' high. Root-lvs. numerous, rosulate, 1 - 3' long, 1/4 as wide, petiolate, pinnatifid or sinuate-dentate, upper ones sublinear and subentire. Fls. middle size (3" long)

Siliques when mature 1 1/2 - 2' long, 1" wide, tipped with a short style. Cotyledons obliqueJy 0= or nearly 0||. Apr., May. 0. A variety (A. petraea Lam.?) has very slender, upright stems, smooth, a few small, incised root-lvs., few linear stem-lvs. and cotyledons wholly 0=.- Shores of the great lakes (Ohio), Can.

3 A. Thaliana L. Mouse-ear Cress. Sts. branched at base, erect; lvs. pilous, oblong, nearly entire; petals twice longer than calyx; pods erect, squarish.-Crucifeeae Crucifers Part 4 256 Bocks and sandy fields, Vt. to Ill. and Car. Whole plant pubescent with stellate-hairs. St. several from the same root, erect, simple, slender, 4 - 12' high. Root-lvs. rosulate, petiolate, 1 - 2' long, cauline appressed, an inch long, base somewhat clasping. Fls. small, white. Pods 6 - 8" long. Cotyledons obliquely 0|. May. § Eur. (Sisymbrium, Gay.)

4 A. dentata Torr. & Gr. Sts. branched at base, diffuse; lvs. roughish-downy, oblong, sharply toothed; petals hardly longer than calyx; pods spreading.-Crucifeeae Crucifers Part 4 257 River banks, N. Y. to Mo. Plant scabrous with stellate hairs. Sts. decumbent, a foot high. Root-lvs. 2' long by 3/4; cauline half-clasping with an auriculate base, all very obtuse and irregularly toothed. Fls. small, whitish. Pods very Blender, 1' long. May.

5 A. patens Sullivant. Erect, pubescent; cauline lvs. coarsely toothed; siliques spreading and curved upwards, beaked with a distinct style. - Rocky banks of the Scioto, 0. (Sullivant), and southward. Sts. 1 - 2f high- Root-lvs. rosulate, petiolate; stom-lvs. oblong-ovate or linear, auriculate-clasping. Fls. rather large (5 - 6" broad), white. Pods nearly 2' long. May.

6 A. hirsuta Scop. Erect, hirsute; radical lvs. oblong-ovate, tapering to a petiole, cauline oval or lanceolate, sagittate-clasping, entire or toothed; siliques straight, erect; sty. none.-Crucifeeae Crucifers Part 4 258 Found in low, rocky grounds, Can. to Va., W. to Oregon. Sts. 2 or more from the same root, round, hairy at base, near a foot high, slender and parallel. Lvs. scarcely dentate, sessile, with heart-shaped or arrow-shaped bases, the upper acute. Fls. greenish-white. Siliques 1 - 2' long. Jn.

7 A. laevigata DC. Tall, glaucous, smooth; stem-lvs. linear-lanceolate, and linear, sagittate-clasping, the upper entire; siliques very long, linear, at length spreading and pendulous.-Crucifeeae Crucifers Part 4 259 In rocky woods and low grounds, Can. to Tenn. and westward. St. 2f high, round, simple, or branched above. Root-lvs. often purplish, obovate and oblong, petiolate, 3/4 - 1 1/2' long, 1/3 as wide, with acute teeth. Stem-lvs. 3 - 5' long and very narrow. Fls. erect, greenish, the petals hardly longer than the calyx. Siliques 3' long, scarcely 1" wide. May.

8 A. Canadensis L. Sickle Pod. Tall, pubescent; stem lvs. lanceolate, pointed both ways, sessile; silique subfalate, veined, pendulous.-Crucifeeae Crucifers Part 4 260 On rocky hills Can. to Ga., W. to Ark. A plant remarkable for its long, drooping pods which resemble a sickle-blade, or rather a scythe. St. 2 - 3f high, slender, round, smooth. Lvs. 3 - 5' long, 1/4 as wide, the lowest early marescent, middle and upper ones sessile or clasping, with narrow bases, remotely denticulate. Fls. small, the narrow, white petals twice longer than the calyx. Pods slender, flattened, 3' long. May, Jn.

8. CHEIRANTHUS, L. Wall Flower. (Arabic kheyry, the name of a certain plant, and Gr. avθoς, flower.) Calyx closed, 2 of the sepals gibbous at base; petals dilated; silique terete or compressed; stigma 2-lobed or capitate; seeds flat, in a single series, often margined. (0 = ). Garden perennials, mostly European. Lvs. undivided.

C. Cheiri L. St. somewhat shrubby and decumbent at base; lvs. entire or slightly dentate, lanceolate, acute, smooth; branches angular; petals obovate; siliques erect, acuminate.-Crucifeeae Crucifers Part 4 261 From S. Europe. A popular garden flower, admired for its agreeable fragrance, and handsome corymbous clusters of orange or yellow flowers. Plant about 2f high. Jn.†

9. LEAVENW6RTHIA, Torr. (Named for Br. Leavenworth, the discoverer.) Calyx rather erect; petals cuneate, retuse or truncate; silique flat, linear or oblong, valves indistinctly veined; seeds in a single row, flattened, wing-margined; embryo nearly straight, curving towards an accumbent form.-Crucifeeae Crucifers Part 4 262 Low, smooth herbs with lyrate-pinnatifid lvs. Fls. yellowish.