186 IMPORTANT FAMILIES OF PLANTS 



developed industry in some parts of the country. It is not known 

 when the cabbage was first used as food. It is referred to in 

 literature antedating the Christian Era by about three hundred 

 years, and it is now very generally used throughout the world. 

 There are many important commercial varieties. These may 

 be classified into (a) the early or short-season group, with 



FIG. 114. The spherical form of cabbage. 



small round or pointed heads, as Jersey Wakefield; (6) the late 

 or long-season group, with large round or flat heads, as Drum- 

 head and Flat Dutch. All endure spring and fall frosts. 



Cauliflower (Fig. 115), Brussels sprouts, Kale and Kohl-rabi 

 (Fig. 116) are derived from the same wild plant. 



Mustards (B. alba Gray and B. nigra Koch). These well- 

 known plants are annuals and produce seeds of considerable com- 



