554 BOTANY. 



Race V. Kohl-Rabi, in which the short and few-leaved stem becomes 

 thick, bulbous, and edible. 



B. campefttris, of the same regions as the preceding, has given rise to 

 the various kinds of Turnips. Colza and Rape ali-o are probably vari- 

 eties ; the latter are extensively cultivated in Europe for their oily 

 seeds, from which useful oils are obtained by pressure. 



Raphanus sativus, the Radish, is a native of China. 



Nasturtium Armoracia, the Horseradish of Europe, has long been 

 cultivated for its pungent roots, which are used as a condiment. Ac- 

 cording to Dr. Gray, the plant, for some unknown reason, does not pro- 

 duce seeds in this country. 



JV. officinale, Water Cress of Europe, and now run wild in many parts 



Fies. 536-41. SEEDS OF CKUCIFEIUG. 



Fie. 537. 



FIG. 541. 

 Fie. 539. 



Fig. 536.- Seed of Erysimum. Magnified. 

 Fig. 537. Longitudinal section of seed. Magnified. 



Fig. 538. Cross-section of seed, showing incumbent cotyledons. Magnified. 

 Fig. 539. -Longitudinal section of seed of Arabia. Magnified. 

 Fig. 540. Cross-section of eeed of Arabi*, accumbent cotyledons. Magnified. 

 Fig. 541. Cross-section of seed of Barbarea, imperfectly accumbeut cotyledons. 

 Magnified. 



of the United States, and many other rapidly growing foreign and na- 

 tive species, are used as salads. 



Brasslea alba, White Mustard, and B. nigra, Black Mustard, both 

 natives of Europe, are grown for their seeds, which when ground con- 

 stitute the common condiment Mustard. It is also of considerable 

 value in medicine. 



Isatis tinctm ia, a tall-growing European biennial, was formerly ex- 

 tensively grown for the blue dye obtained from it. 



The most important ornamental plants of the order are the Wall- 

 flower (Cheiranthus), Gilly Flower or Brompton Stock (Matthiola}, 

 Rocket (Hesperid), Candytuft (Iberis), Honesty (Tsunaria), Sweet Alys- 

 Bum (Alyasum), etc., etc. 



Several of the species are troublesome weeds eg., Shepherd's Purse 

 (Gapselld), which has come to this country from the Old World ; Pepper- 

 grass (Lepidium), native and introduced ; False Flax ((Jamelirui) from 

 Europe ; Charlock and Mustard (Brassicd) from Europe. 



