CRVCIFKR^E. 31, 



3. N. sylvestre Brown : leaves pinnate ; leafets lanceolate, cut, the upper- 

 most ones entire. Sisymbrium sylvestre Linn. S. vulgare Pers. 



Banks ol the Delaware, near Philadelphia. Null. July 1\.. Root creeping. 

 Stem a foot liigh, angular, branched. Flowers yellow, larger than those of the 

 preceding. Introduced from Europe. Creeping Cress. 



4. N. amphibium Broicn : root fibrous ; leaves oblong-lanceolate, lyrate- 

 pinnatifid or serrate ; petals longer than the calyx ; pod elliptical, tipped 

 with the mucronate style. Sisymbriiim amphibium Linn. 



Wet places. Throughout the U. S. and Can. May July. 1\.. Stem 12 

 feet high, branched. Flowers yellow, minute, in a long raceme. Very variable 

 in the character of its leaves. Water Radish. 



5. N. hispidum D. C. : leaves pinnatifidly lobed or runcinate-pinnatifid ; 

 lobes rather obtusely toothed ; pod ovoid, tumid, pointed with the distinct 

 style, about half as long as the pedicel , petals rather shorter than the calyx. 

 Sisymbrium hispidum Pair. 



Wet places. Conn. N. Y. Penn. July, Aug. 7J.. Stem 24 feet high, 

 much branched above. Leaves more or less pinnalifid. Flowers yellow, in nu- 

 merous panicled racemes. Hispid Cress. 



6. N. natans D. C. : emerged leaves oblong-linear, entire ; immersed ones 

 cut into many capillary segments ; petals scarcely longer than the calyx ; 

 pod obovate, globose. 



In water. Montreal to New Orleans : rare. July. %. Stem long, sub- 

 merged. Lower leaves finely divided ; middle ones often pinnatifid ; emerged 

 ones lanceolate, undivided, serrate. Flowers pale yellow, small. According to 

 Torrey and Gray the American plant is a variety of the foreign one. 



Floating Cress. 



16. TURRITIS. DHLTower Mustard. 



(From the Latin turris, a tower; on account of the pyramidal form of the 

 plant.) 



Pod linear ; the valves plane. Seeds in a double row in each 

 cell. Flowers white or rose-color. 



T. stricta Graham: smooth; stem straight and erect; cauline leaves 

 linear-lanceolete clasping and sagittate, sparingly toothed ; radical petioled, 

 narrow-spatulate, remotely denticulate ; pods linear, elongated and (like the 

 flowers) strictly erect. 



On rocks. Jefferson and Chenango counties, N. Y. W. to the Rocky Moun- 

 tains. May. (g). Stem 1 2 feet high, simple. Flowers in a terminal raceme, 

 white. Pod 2 3 inches long. Straight Tower Mustard. 



17. CHEIRANTHUS. R. Brown. Wall Flower. 



(Said to be derived from the Arabic kheyry, not however originally applied to 

 this genus.) 



Pod terete or compressed. Stigma 2-lobed or capitate. 

 Inner sepals saccate at the base. Seeds in a single series, 

 ovate, compressed. 



C. hesperidoides Torr. <$ Gr. : smooth ; lower leaves lyrate-pinnatifid ; 

 upper ovate-lanceolate, unequally and sharply serrate ; pedicels as long as 

 the calyx ; limb of the petals obovate, entire. Hespera pinnoJifida Mich. 



