150 CRUC1FER.E. 



ing like a single bristle fixed by the middle), or stellately 

 3 - 5-parted ; the stems virgate, leafy. Cauline leaves linear 

 or lanceolate, entire or merely toothed, sessile or short-peti- 

 oled, never dilated and auriculate or clasping at the base ; 

 the radical sometimes runcinate-pinnatifid. Raceme elon- 

 gated in fruit, ebracteate. Flowers yellow, often showy. 



Etymology. 'Epio-ipov, an ancient name, thought to conic from epva, 

 to draiv blisters, in allusion to the acrid properties. 



Geographical Distribution. A pretty large European, and especially 

 North Asiatic genus, of which there are several Western N. American 

 species, but only two or three this side of the Rocky Mountains (excepting 

 E. cheiranthoides, which was doubtless introduced from Europe). The 

 species here illustrated alone crosses the Mississippi, Mr. Sullivant having 

 long since detected it in Central Ohio. 



Note. The areolatiun appears to vary considerably in different species. 

 In E. Arkansanum, the uniform amorphous areolae are bounded by very tor- 

 tuous lines, much as in Turritis. In this species and its near allies, also, 

 the radicle is often oblique, or the cotyledons, in part, almost accumbent. 



PLATE 63. Erysimum Arkansanum, Nutt. ; — summit of a flowering 

 stem ; natural size. (From Ohio, Sullivant.) 



1. Diagram of the flower. 



2. Diagram of the aestivation of the petals at an earlier period (more 



deeply convolute) . 



3. A flower-bud, enlarged. 



4. A lateral, and 5, an anterior sepal, enlarged. 



6. A petal, equally enlarged. 



7. Stamens and pistil, enlarged. 



8. A silique, of the natural size. 



9. Transverse section of the base of a pod, magnified. 



10. Replum, with style and stigma, and three seeds in place, enlarged ; 



two of these cut across to show the cotyledons, which in the lower 

 seed are almost accumbent. 



11. Tissue from the partition, highly magnified. 



