178 CRU'CIFORM PLANTS. 



stamens, it will save you trouble, to remember 

 that the flowers in the class Hexandria never have 

 four petals, while those of the fifteenth class always 

 have that number. The last are generally called 

 Cru'ciform, or cross-shaped, from the four petals 

 being so placed as to form a kind of cross ; and 

 this circumstance forms the natural character of 

 the class Tetradynamia. 



In moist situations, and during wet seasons, the 

 cruciform plants acquire a hot and biting taste, 

 like mustard; but none of them are poisonous 

 Even the common Turnip, Bras'sica Ra'pa, whose 

 root in a dry sandy soil is so sweet and juicy, be- 

 comes, in wet land, hard, and disagreeable to the 

 taste ; and the common Horse-radish, Cochlea'ria 

 Armora'cia, when it grows near water, is so ex- 

 tremely acrid that it can hardly be used. 



The orders of this class, you may remember, 

 are two. They are distinguished from each other by 

 the shape of the seed-vessel, which in both is a Pod. 

 In the first order, Siliculo'sa, the pod is broad and 

 short; and in the second, Siliquo'sa, it is long and 

 narrow. 



The first order contains about twelve native ge- 

 nera: among which are Sea-kale, Cram'be marit'i- 

 ma ; Shepherd's-purse, Thlas'pi Bur'sa-pasto'ris ; 

 Candy-tuft, I'beris ama'ra, which is very often 

 cultivated in flower-gardens ; and common Whit- 

 low-grass, Dra'ba ver'na, a pretty little plant, 



