344 COLLEGE BOTANY 



The turnips (Fig. 182) are of very ancient origin and prob- 

 ably came from Europe but were not very extensively used pre- 

 vious to the seventeenth century. They are now grown through- 

 out a considerable pai-t of the world, especially the north tem- 

 perate zone, and are used as a vegetable and for stock feed. There 

 are three important species, as indicated above, and many vari- 

 eties. The rape is gro'Wn because of the abundant top and is 

 used as a pasture plant for sheep, hogs and cattle. The seeds 

 are also used as a source of oil. 



The radish (Raphanus sativus Linn.) is a well-known early 

 vegetable which probably originated in China, but its early his- 

 tory is unknown. It is extensively cultivated throughout the 

 world, especially in temperate regions. 



The horse-radish (Cochlearia afmoracia Linn.) is another 

 well-known vegetable which is iTsed as a condiment. Its early 

 history is unknown, but it probably originated in eastern Europe 

 and western Asia. 



Nasturtium officinale or water-cress is a well-known salad 

 plant. This family also includes many wild plants, some of 

 which are well known as weeds. Among the most common are 

 the following: Pepper roots (Dentaria sp.), the whitlow grasses 

 (Draba sp.), the shepherd's purse (Capsella, hursa-pastoris) and 

 the pepper grasses (Lepidium sp.). 



Saxifeagace.te (Saxifrage Family). — Herbs or shrubs; 

 leaves alternate or opposite, usually without stipules ; flowers per- 

 fect and usually regular ; sepals four or five ; petals four or five, 

 inserted on the calyx; stamens ten, many (rarely five) and in- 

 serted on the caJyx; ovary compounds, inferior or partly in- 

 ferior ; fruit a two- to many-celled capsttle or true berry. 



The most important economic plants of this family are the cxw- 

 rant and gooseberry, both belonging to the genus Ribes. The most 

 important of our cultivated gooseberries (Fig. 183) and currants 

 came from Europe. Llowever, there are many ornamental plants, 

 such as mock orange and hydrangea, belonging to this family. 



