Arabis. . CRUCIFERiE. 81 



6. A. ambigua (DC): leaves nearly glabrous, the radieal ones sinuate- 

 lyrate ; middle ones oblong-oval and toothed, attenuate at the base ; the up- 

 permost linear-oblong and entire ; stem nearly simple ; sihques soinevviiat 

 erect. — DC. sijsl. 2. p. 231 ; Cham, df- iSchlcclil. in LinncBa, 1. p. 10; Jluuk. 

 fl. Jim:- Am. l./J. 42. 



Unalaschka, Sitcha ! and Kotzebue's Sound.—® Stems numerous from 

 one root, a foot or more high, ascending. Radical leaves with a few simple 

 hairs ; cauline ones very glabrous. Racemes few-flowered ; the flowers 

 smaller than in the preceding species. Silique two inches long and nearly a 

 line broad, pointed with the nearly sessile stigma. Seeds without a border ; 

 the cotyledons distinctly accumbent. 



7. A lyrata (Linn.): stem branching from the base; radical leaves 

 lyrate-pinnatifid and somewhat hirsute ; cauline ones linear, entire, and 

 with the stem glabrous ; siliques erect, nearly straight ; radicle slightly dor- 

 sal.— /-'?w.b7(,/. 2. /). 437 ; DC. prodr. \. p. 146. Sisymbrium arabidoides, 

 Hook. ! fl. Bor.-Am. 1. p. 63. t. 1 ; DarUngl. fl. Cest. ed. 2. p. 387. 



On rocks, Canada ! to Virginia! April-May.— (T) Stem 4-12 inches high, 

 at first erect, but at length difluse. Radical leaves rosulate in the yourig 

 plant ; the segments usually obtuse, often toothed. Flowers as large as in 

 A. petra^a, white. Mature siliques 1^-2 inches long, scarcely more than 

 lialf a line broad, pointed with a short style. Seeds without a border. Coty- 

 ledons flat, ovate ; the radicle lying along the edge of one of them, so as to 

 be nearly accumbent. — Our excellent friend Sir William J. Hooker refers 

 this plant to Sisymbrium ; but we retain it in Arabis, because, on a careful 

 examination of numerous ripe seeds, we find the radicle so slightly dorsal 

 that the cotyledons may be regarded as accumbent. We have never seen 

 the seeds so evidently incumbent as they are represented in Hooker's figure. 



8. A. rupestris (Nutt. ! mss.) : " more or less hirsute ; radical leaves ob- 

 long-spatukte ; cauline ones lanceolate, clasping, sparingly toothed ; petals 

 twice as long as the calyx ; silique very long and narrow, erect-spreading. 



" On rocks near the'banks of the Oregon.— @ Plant li-2 feet high ; the 

 pubescence simple or forked : upper part of the stem nearly smooth. Cauline 

 leaves clasping, but not sagittate. Siliques about 3 inches long, less than a 

 line in breadth. Seeds slightly margined." Nutt. — Near A. saxatilis. 



9. A. spathulata (Nutt.! mss.): "hirsute (dwarf and somewhat ca^spitose); 

 leaves spatulate-oblong, entire ; cauline ones clasping ; petals roundish, 

 spreading, about twice the length of the calyx; siliques rather short, diverg- 

 ing, pointed with a distinct slender style. 



" Lofty dry hiUs of the Platte, from the Black Mountains to the central 

 chain. May.— If About 4 inches high. Root thick, crowned with vestiges 

 of former leaves and stems. Radical leaves on rather long petioles. Flow- 

 ers white, somewhat conspicuous. Pedicel about half the length of the 

 fruit. Silique scarcely half an inch long and nearly a line in breath ; cells 

 7-10-seeded." Nutt. Seed oblong, with a narrow margin. Funiculus long 

 and slender, free. — Near A. serpyllifolia of Europe. 



10. A. heterophylla (Nutt. mss.) : " nearly smooth; radical leaves spatu- 

 late, toothed ; upper ones linear, sessile, entire ; silique long and spreading ; 

 petals linear-oblong, exceeding the calyx. 



" Near Paris, Maine ? or in the vicinity of the White Mountains of New- 

 HampsMre. — (|) Radical leaves s6mewhat pilose with simple hairs ; upper 

 ones' linear, about 2 inches in length and a line or two in breadth. Siliques 

 about 3 inches long." Nutt. — We have seen no specimens of this plant. 



11. A. sparsiflora (Nutt. mss.): "somewhat pilose towards the base, 

 much branched ; cauline leaves oblong, clasping, entire; flowers minute; 

 siliques very long, flat; spreading. 



11 



