54 CRUCIFER^. Arabis. 



Root biennial. Stem 12-18 inches high, simple, or branched at the base, often smooth 

 on the upper part. Radical leaves an inch or more long, and 3-5 lines wide, more or less 

 distinctly toothed. Flowers greenish-white, when fully expanded about 3 lines in diameter. 

 Siliques straight, 1-2 inches long, tipped with the nearly sessile stigma. Seeds with a 

 narrow margin. 



Rocky places; rare. May. — In the young state, and when smoother than usual, this 

 species often resembles A. Icevigata, but differs in its smaller size, proportionably wider leaves, 

 and in its pubescence of which more or less is found on the leaves and lowet part of the stem. 

 In fruit they are easily distinguished. 



2. Arabis dentata, Torr. Sf Gr. Toothed Wall Cress. 



Plant more or less rough with a stellate-pubescence ; radical leaves obovate, tapering at 

 the base into a petiole which is as long as the lamina, irregularly dentate with sharp salient 

 teeth ; cauline ones oblong, clasping ; flowers minute ; petals spatulate, scarcely longer than 

 the calyx ; siliques short, spreading, on very short pedicels, pointed with the nearly sessile 

 stigma ; stem branched from the base. — Torr. ^ Gr.fi. N.Am. I. p. 80. Sisymbrium den- 

 tatum, Torr. in Shorfs 3rd suppl. cat. pi. Kentucky. 



Root annual. Plant a foot or more in height : the pubescence, particularly of the under 

 surface of the leaves, short and rather scabrous. Stem slender, often decumbent at the base. 

 Radical leaves 2 inches long and three-quarters of an inch wide ; cauline ones auriculate at 

 the base, irregularly toothed. Flowers scarcely 2 lines long. Sepals and the very short pe- 

 dicels, hirsute. Petals dusky white. Silique an inch long ; valves somewhat convex. Seeds 

 slightly margined. Radicle long and slender, distant from the accumbent cotyledons. 



Near Utica {Dr. Gray). May. A rather common species in the western States. 



3. Arabis lyrata, Linn. Lyre-leaved Wall Cress. 



Stem branching from the base ; radical leaves lyrate-pinnatifid and somewhat hairy ; cau- 

 line ones linear, or spatulate, entire, and with the stem smooth ; siliques rather erect, nearly 

 straight ; radicle slightly dorsal. — Pursh,fl. 2. p. 327; DC. prodr. 1. p. 146; Torr. <J- Gr. 



fl. N. Am. 1. p. 81. Sisymbrium arabidoides. Hook. fl. Bor.-Am. 1. p. 63. t. 1 ; Darlingt. 



fl. Cest. p. 387. 



Root biennial. Stems usually divided to the root, or rather several from one root, 4-12 

 inches high, at first erect, but at length much branched and diffuse. Radical leaves of the 

 young plant in a circular cluster, 1-2 inches long, obovate in the outline, usually lyrate- 

 pinnatifid, with rounded and mostly entire lobes, but often only toothed. Flowers about five 

 lines in diameter, white or rarely pale purple. Petals obovate. Siliques about an incii and 

 a half long, very slender ; pedicels about one-fourth the length of the siliques. Seeds with- 

 out a border. Cotyledons flat, ovate ; the radicle lying along the edge of one of them, so as 

 to be nearljr accumbent. 



Common on rocks ; flowering in April and May, and, in shady situations, sometimes until 

 August. 



