70 THE CRUCIFORM FAMILY. 



useful plants in this Tribe : being tbe mustard used at 

 our tables. It is, in appearance very like the Tur- 

 nips ; but is placed in a separate Genus : from having 

 a spreading calyx (patent) instead of erect; and 

 smooth, quadrangular pods ; with narrow upper leaves, 

 by which differences you can distinguish it perhaps ; 

 but these yellow-flowered Mustards and Turnips are 

 so similar that it is rather difficult to identify them 

 sometimes. 



Another MUSTARD; CHARLOCK, (S. arvensis) is a 

 troublesome weed to the farmer; but doubtless, many 

 a bird and insect, find it a valuable food and shelter. 

 Its flowers are yellow, leaves large, bristly and dark, 

 stem 1 to 2 feet high, rough, pod smooth, with many 

 angles, turged and knotty, longer than the slightly 

 compressed Beak. 



The WALL-ROCKET. (Diplotaxis tenuifolia,) has 

 pale yellow flowers, as large as the Wall -flower; with 

 long, narrow leaves. Not a common plant but 

 adorning many a ruin ; and nowhere can it be looked 

 upon with greater interest than on the venerable ruins 

 of St. Alban's Abbey, where 



" Still she seeks, with kind, unceasing aid, ' 



To hide the fearful wreck which ruthless time has made." 



