176 



CRUCIFERAE. 



Vol. II. 



I. Arabidopsis Thaliana (L.) Britton. Mouse-ear 

 or Thale-cress. Wall-cress. Fig. 2063. 



Arabis Thaliana L. Sp. PI. 665. I753- 



Sisymbrium Thalianum Gay, Ann. Sci. Nat. 7; 399- 1826. 



Stenophragma Thaliana Celak. OEster. Bot. Zeitsch. 27: I77. 

 1877. 



Annual, stem slender, erect, i'-i6' high, freely branching, 

 more or less pubescent with short stiff hairs, especially 

 below. Basal leaves 1-2' long, obtuse, oblanceolate or 

 oblong, narrowed into a petiole, entire or slightly toothed; 

 stem-leaves smaller, sessile, acute or acutish, often entire; 

 pedicels very slender, spreading or ascending, 2"-4" long 

 in fruit; flowers about i*" long; petals about twice the 

 length of the sepals; pods narrowly linear, 4"-io" long, 

 acute, often curved upward, glabrous. 



In sandy fields and rocky places, Massacusetts and southern 

 Ontario to Minnesota, Georgia, Missouri, Arkansas and Utah. 

 Very common eastward. Naturalized from Europe. Native 

 also of northern Asia. Turkey-pod. April-May. 



2. Arabidopsis novae-angliae (Rydb.) Britton. Low or Northern Rock-cress. 



Fig. 2064. 



Arabis pelraea Hook. Fl. Bor. Am. i : 42, in part. 1829. 

 Not Lam. 



Sisymbrium humile Wats. & Coult. in A. Gray, Man. Ed. 6, 

 71. 1890. Not Meyer, 1831. 



Braya humilis Robinson, in Gray & Wats. Syn. Fk i' : 141, 

 in part. 1895. 



Pilosella novae-angliae Rydb. Torreya 7; 158. 1907. 



Perennial, erect, 4'-io' high, branching below, spar- 

 ingly pubescent. Leaves spatulate, or oblanceolate, the 

 lower obtuse, 1-2' long, narrowed into a petiole, sharply 

 dentate or rarely entire, the upper smaller, narrower, 

 often acute; flowers white or pink, li"-2" broad; pedi- 

 cels ascending or erect, 2"-3" long in fruit; pods nearly 

 terete, glabrous, narrowly linear, 6"-io" long, I" wide ; 

 valves finely nerved; style i" long. 



In rocky places, Anticosti, Willoughby Mountain, Vt., 

 near Michipicoten Harbor, Lake Superior. July. 



31. BARBAREA R. Br. in Ait. Hort. Kew. Ed. 2, 4: 109. 1812. 



Erect glabrous biennial or perennial branching herbs, with angled stems, pinnatifid 

 leaves, and racemose yellow flowers. Stamens 6. Silique elongated, linear, 4-angIed, the 

 valves keeled or ribbed. Style short. Stigma 2-lobed or nearly capitate. Seeds in I row 

 in each cell, flat, oblong, marginless ; cotyledons accumbent. [Name from St. Barbara, to 

 whom the plant was anciently dedicated.] 



A genus of about 7 species, natives of the temperate zones. Besides the following, another 

 occurs in western North America. Type species : Barbarea vulgaris R. Br. 



Pods obtusely 4-angled, slender-pedicelled ; leaf-segments 1-4 pairs. 



Pods divergent or ascending. i. B. Barbarea. 



Pods erect, appressed. . 2. B. striata. 



Pods sharply 4-angled, stout-pedicelled ; leaf-segments 4-8 pairs. 3. B. vcrna. 



