MUSTARD FAMILY. 219 



purplish, erect and equal, or the lateral pair slightly saccate at base. 

 Petals obovate or spatulate, with narrow claw and flat blade, com- 

 monly much exceeding the sepals. Pod flattened parallel to the 

 partition, the valves more or less 1-nerved. Seeds more or less 

 winged; cotyledons accumbent, or in one species partially incumbent. 

 (Name from the land Arabia.) 



Leaves all pinnately parted; plants decumbently branching from the base; 



flowers small, white 1. ^. Virginica. 



Leaves entire, toothed or only the radical plnnatifid. 

 Tall biennials with white flowers ; sepals greenish. 



Glaucous; glabrous except at the base . -.■ 2. A. glabra. 



Not glaucous; hirsute throughout 3. A.'Mrsata. 



Low, more or less tufted perennials ; sepals purplish , rarely greenish. 

 Herbage dark green, mostly glabrous; pods nearly straight; seaboard 



species i. A. blepharophylla. 



Herbage more or less canescent; pods arcuate; montane species. . . . 



5. A. Breweri. 



1. A. Virginica (L.) Trelease. Annual or biennial, nearly gla- 

 brous; branched from the decumbent base, the branches 7 to 15 in. 

 high; leaves deeply pinnatifid with nearly uniform oblong or linear 

 few-toothed or entire segments; flowers small, white, on very short 

 pedicels; pods spreading, f to 1 in. long, 1 line broad, borne on ped- 

 icels 1 to 2 lines long, beaked by a short pointed style; valves faintly 

 veined or obscurely 1-nerved at base; seeds in 1 row. — (A. Ludo- 

 viciana C. A. Mey.) 



Lower San Joaquin Eiver banks, Sanford; probably introduced 

 from Southern California. 



2. A. glabra (L.) Bernh. Tower Mustabd. Biennial, erect, 

 simple (very rarely branched), 2 to 4 ft. high; herbage glaucous, at 

 the base hispidulous, above glabrous; radical leaves broadly spatulate, 

 coarsely dentate or merely denticulate, 2 to 4J in. long, soon wither- 

 ing; cauline leaves ovate or ovate-lanceolate, entire, clasping by a 

 sagittate base; flowers dull white, 2 to 3 lines long, little exceeding 

 the sepals; pods strictly erect, even appressed to the stem, straight, 3 

 to 4 in. long, J to f line wide, on pedicels 3 to 5 lines long; seeds in 

 2 rows, narrowly winged or wingless. — (A. perfoliata Lam.) 



Throughout California: not rare, but the plants commonly solitary. 

 Apr. -May. 



3. A. hirsuta Scop. Hairy Eock Cress. Biennial, more or 

 less hirsute, deep green, not glaucous; stems erect, simple or strictly 

 branched, 1 to 3 ft. high; radical leaves oblanceolate, the petioles 

 winged, 1 to 2 in. long; cauline oblong to lanceolate, commonly 

 entire, sessile by a subeordate base; petals dull white, IJ to 3 lines 

 long; pods strictly erect on slender pedicels, 1 to 2 in. long, J line 

 wide; style scarcely any; valves faintly nerved below the middle and 

 more or less veined; seeds suborbicular, very narrowly margined. 



Northern California: Marin Co. (aec. to G-reene). 



4. A. blepharophylla H. & A. Biennial or perennial, branched 

 at base or simple, 4 to 12 in. high, deep green, glabrous, or somewhat 

 hirsute below; radical leaves broadly spatulate to obovate, obtuse, 



