June, I'.il (J The Brassicacece of Ohio 323 



20. Arabis L. Rock-cress. 



Annual or biennial erect, glabrous or pubescent herbs, with 

 entire or lobed, sometimes pinnatifid leaves, and white or 

 purple flowers in racemes. Siliques linear, dehiscent. Seeds 

 in 1 or 2 rows in each cavity, winged or wingless. 



1. Flowers white. 2. 



1. Flowers purple or puqjlish; basal leaves spatulate; stem-leaves lanceolate. 8. 



2. Basal and stem-leaves similar, pinnatifid; plant glabrous. A. virginica. 



2. Basal and stem-leaves different. 3. 



3. Basal leaves lyrate; stem-leaves spatulate to linear; plant glabrous above, 



pubescent below. ,1. lyrata. 

 3. Basal leaves on marginal petioles; stem-leaves clasping; plant pubescent. 4. 



3. Basal leaves petioled. 6. 



4. Petals as long as the calyx. 5. 



4. Petals longer than the calyx; pods erect or appressed. A . hirsuta. 



5. Flowers greenish white; pods spreading. A.dentata. 



5. Flowers bright white; pods ascending. A. patens. 



6. Plant glabrous and glaucous; stem-leaves clasping; petals slightly longer than 



the calyx; pods long. 7. 



6. Plants glabrous above, pubescent below; stem-leaves not clasping; petals 



twice as long as the calyx; pods scythe-shaped. A. canadensis . 



7. Petals yellowish-white; pods appressed. .4. glabra. 



7. Petals greenish-white; pods recurved-spreading. A. laevigata. 



8. Plant glabrous and somewhat glaucous; pods close, erect. A. drummondii. 

 8. Plant glabrous above; purple-glaucous; pods spreading. A. brachycarpa. 



1. Arabis dentata T. & G. Toothed Rock-cress. Stems 

 slender, upright, branching from the base, 1-2 ft. high; leaves 

 broad-ovate or obovate, dentate, basal leaves 2-4 in. long, 

 stem-leaves auricled; pods linear, ascending; seeds marginless, 

 in 1 row in each cavity. 



An indigenous biennial or perennial. Rather general. 



2. Arabis patens Sull. Spreading Rock-cress. Stem simple, 

 erect, leafy, 1-2 ft. high, densely pubescent; basal leaves dentate, 

 1-3 in. long, stem-leaves sessile, cordate-clasping, ovate or 

 oblong, the middle ones largest ; pods narrow, flat ; seeds narrowly 

 winged, in 1 row in each cavity. 



An indigenous biennial. Franklin County. 



3. Arabis hirsixta (L.) Scop. Hairy Rock-cress. Stem 

 erect, nearly simple, rough-hairy or nearly glabrous, 1-2 ft. 

 high; basal leaves obovate, obtuse, dentate, 1-2 in. long on 

 margined petioles; stem-leaves lanceolate or oblong, partly 

 clasping by a somewhat heart-shaped base; pods linear, 1-2 in. 

 long; seeds narrowly winged, in 1 row in each cavity. 



A European biennial, in rocky places. Rather general. 



4. Arabis glabra (L.) Bernh. Tower Mustard. Stems erect, 

 usually simple or branched at the base, 2-4 ft. high, glabrous 



