CRUCIFER^ 345 



The genus is one of wide distribution; it is most abundant 

 in the north temperate zone. 



There is a rather large number of species, some of which are 

 amphibious, others aquatic. The two principal economic 

 species are Radicula armoracia (horse-radish) and Radicula 

 nasturtium-aquaticum (water cress) . The former is terrestrial, 

 the latter aquatic. 



RADICULA ARMORACIA 



(Horse-radish) (Fig. 144)] 



Description. — Horse-radish is a hardy perennial from a 

 white, fleshy, cylindrical root which branches at the lower, 

 end. The fibrous roots may penetrate to a depth of 6 or 7 

 feet. In propagating the plant, the slender side roots usually 

 are used; pieces of the main root are also used for this purpose. 

 The plants are 2 to 3 feet tall, branching, with long-petioled, 

 oblong, basal leaves, 6 to 12 inches long, that have crenate, 

 sinuate or pinnatifid margins. The upper leaves are smaller, 

 sessile, oblong, or lanceolate. The racemes are terminal or 

 axillary, and bear white flowers. The pods are oblong or 

 nearly globose and bear a short persistent style. In cultiva- 

 tion, the plant seldom produces seed, but is propagated by 

 root cuttings. 



Geographical. — Horse-radish is a native of Europe. It is a common liome 

 garden plant in the United States, and in some instances has escaped from 

 cultivation and become a troublesome weed. 



Uses. — The root is grated or scraped, sometimes mixed 

 with vinegar, and used as a condiment. 



RADICULA NASTURTIUM-AQUATICUM 

 (Water Cress) 



Description. — This is a perennial, aquatic plant with long 

 floating or creeping stems which readily take root at the 



