66 CRUCIFER.E, (mustard FAMILY.) 



§ 1. ARABIS proper. Seeds in one row in each cell, orbicular or nearly so, 

 more or less wing-margined ; cotyledons strictly accambent. 

 * Low, chiefly biennials, diffuse or spreading from the base. 



1. A. Ludoviciana, Meyer. Nearly glabrous, often aimual ; leaves all 

 pinnately parted iuto oblong or linear few-toothed or entire divisions, those of 

 the lower leaves numerous ; pedicels very short ; flowers small, white ; pods 

 rather broadly linear, spreading, flat ; seeds winged. — Open grounds, Va. to 

 Mo., and southward. 



* * Erect and simple leafy-stemmed biennials, with simple leaves, white or 

 whitish flowers, narrow but flattened ascending or erect pods, and nearly 

 wingless seeds. 



2. A. pktens, Sulliv. Downy with spreading haii-s, erect (1-2° high); 

 stem-leaves oblong-ovate, acutish, coarsely toothed or the uppermost entire, 

 partly clasping by tlie heart-shaped base ; petals (bright white, 4" long) twice 

 the length of the calyx ; pedicels slender, spreading ; pods spreading or ascend- 

 ing, tipped with a distinct style. — Peun. to central Ohio and southward ; Minn. 

 April, May. 



3. A. hirstlta, Scop. Rough-hairy, sometimes smoothish, strictly erect 

 (1-2° high) ; stem-leaves oblong or lanceolate, entire or toothed, partlv clasp- 

 ing by a somewhat arrow-shaped or heart-shaped base ; petals (greenish-white) 

 small, but longer than the calyx; pedicels and pods strictly upright; style 

 scarcely any ; immature seeds somewhat 2-rowed. — Rocks, common, especially 

 northward. May, June. (Eu.) 



« * * Erect and simple leafy-stemmed biennials (1 -3° high), icith small ichitish 

 flowers, recurved-spreading or pendtdous flat pods (3-4' long), and broadly 

 winged seeds, their stalks adherent to the partition ; root-leaves rarely lyrate. 

 4 A. laevigata, Poir. Smooth and glaucous, upright ; stem-leaves partly 

 clasping by the arrow-shaped base, lanceolate or linear, sparingly cut-toothed or 

 entire ; petals scarcely longer than the calyx ; pods long and narroiv, recurved- 

 spreading ou ascending or merely spreading pedicels. — Rocky places, Maine 

 to Minn, and soutliward. May. 



5. A. Canadensis, L. (Sickle-pod.) Stem upright, smooth above; 

 stem-leaves pubescent, pointed at both ends, oblong-lanceolate, sessile, the lower 

 toothed ; petals twice the length of the calyx, oblong-linear ; pods very flat, 

 scythe-shaped, hanging on rough-hairy pedicels (2" wide). — Woods and ravines ; 

 not rare, especially westward. June - Aug. 



§ 2. TURRITIS. Seeds not so broad as the partition, in two more or less 



' distinct rows in each cell, at least when young; strict and very leafy. 



stemmed biennials ; cauline leaves partly clasping by a sagittate base. {Our 



species very glabrous, except the mostly hirsute base of the stem and the lower 



leaves.) 



6. A. perfoli^ta, Lam. (Tower Mustard.) Tall (2-4° high), 

 glaucous; stem-leaves oblong or ovate-lanceolate, entire; petals yellowish- 

 white, little longer than the calyx ; pods very narrow (3' long) and pedicels 

 strictly erect ; seeds marginless ; cotyledons often oblique. — Rocks and fields, 

 N. Eng. to Minn, (rare), north and westward. (Eu.) 



