TETRADYNAMIA SILIQUOSA 387 



calyx; pedicels slender, spreading, longer than the siliques. Hook. 



Am. I. p. 62. 



S. Sophia? Muhl. Catal. p. 61. Pursh, Am. 2. p. 440. Torr. 



Comp. p. 251, Beck, Hot. p. 33. Not of Linn. DC. &c. 



Hoary Sisymbrium. 



Plant pale green and somewhat glaucous, or canescent. Root annual, terete, 

 tapering, with a few coarse branches. Stem 1 to 2 feet high, subterete, smooth ish 

 vxry pale green, or whitish, more or less branched, often much branched from 

 near the base. Leaves I to 3 or 4 1 nches long, bipinnately and rather finely dis- 

 sected, smoothish, or sparingly pilose, pale green, or glaucous; segments of the 

 lower leaves ovate-oblong and obovate, mostly obtuse, incised-dentate,— of the 

 uppv leaves lance-linear, incised-serrate, or.enlire (the uppermost leaves often 

 simply and deeply pinnatifid, with narrow sublinear entire segments half an inch 

 to 3 quarters in length) ; petioles short, dilated, nerved. Racemes slender, 4 to 

 12 or 15 inches long; pedicels half an inch to an inch long, slender, spreading. 

 Petals pale yellow, or ochrolcucous, obovate-oblong, small, about as long as the 

 calyx. Siliques about half as long as the pedicels, linear-oblong, abruptly acute, 

 rather erect, or ascendiug, often slightly curved, smooth ; valves with a central 

 keel-like nerve. Seeds ovate-oblong, striate-punctate, reddish brown. 



Hab. Banks or the Schuylkill ; Black Rock: rare. Fl. May. Fr. June. 



Obs. This has been found only In the above locality, In Chester County, —where 

 it was collected by Mr. John Marshall, in 1829. I collected specimens cf it on 

 the banks of the Potomac, near Georgetown, in 1820; and Mr. Schtoeinitz pro- 

 nounced them to be a variety of S. canescens. Our plant, however, is much less 

 pubescent and hoary than the true S. ca?icsce?is of the Southern States,— and the 

 siliques are longer. It is probably the one referred to by Mr. Elliott, in his note 

 on S. canescctts; and I have supposed it may be the var* major, of Pruf. Hooker. 



3. S. arabidoides, Hook. Radical leaves lyrate-pinnatifid, subhir- 

 sute, stem leaves linear, entire, smoothish ; siliques erect, twice as long 

 as the pedicels. Hook. Am. I. p. 63. Icon, tab. 21. 

 Arabis lyrata. L. and the Authors quoted in this -work. 

 Also ? A. hispida. Muhl. Catal. p. 61. Not of Linn. 



Arabis-like Sisymbrium. 



Root perennial, Nutt. biennial, Torr. Beck, annual, Willd. Hook, somewhat 

 fusiform. Stem 6 to 12 inches high, branched, often numerous from the same root, 

 flexuose, striate, hispid at base, smooth above, and somewhat glaucous. Radical 

 leaves numerous and tufted, 1 to 2 or 3 inches long, and 1 fourth to half an inch 

 wide, lyrate-pinnatifid, hirsutely pilose and ciliate, petiolate ; lower stem-leaves 

 oblong, tapering at base to a petiole, pinnatifid and sinuate-dentate, more or less 

 pilose ; upper ones half an inch to an inch and half long, and 1 to 2 lines wide, 

 aublinear, narrowed at base, sessile, obtuse, entire, or remotely denticulate, smooth 

 or sparingly pilose. Racemes 2 to 4 or 5 inches long, loose ; pedicels 1 third to 

 half an inch long, spreading. Petals white, or ochrolcucous, rarely tinged with 

 purple, obovate-oblong, spreading, conspicuous, more than twice as long as the 

 calyx. Siliques about an inch long, narrow, linear, rather erect, pointed with a 

 very short style ; valves with a slender keel-like nerve. Seeds oval, reddish 

 brown; cotyledons (obliquely?) incumbent. 



Hab. Dry, rocky hills; Serpentine ridge : frequent. Fl. April-May. Fr. May-June. 



Obs This is abundant on the Serpentine rock; but not very common elsewhere. 



The pubescence is generally long and simple ; but I have seen some specimens 



