WATER CRESS. 227 



Mustard {Sinapis alba), are generally associated in 

 their use as salads, and in their culture in the garden. 

 They are annual plants, and are eaten only when very 

 young. In winter, they may be raised on a slight hot- 

 bed; in spring, under hand-glasses, or in drills near a 

 south wall, and in summer, when they should be sown 

 once a fortnight, in drills, in any cool, shady situation. 

 Table mustard, which is made from the seeds of Sinapis 

 nigra, Lix., belongs rather to the department of agri- 

 culture. Durham mustard, which is distinguished for 

 its poignancy, though not remarkable for fine color, is 

 said to be made principally from the seeds of the com- 

 mon yellow field-mustard or charlock, Sinapis arvensis, 

 LiN. 



■ Water Cress {Sisymbrium nasturtium). — This is a 

 creeping perennial aquatic plant, very extensively sup- 

 plied in the English markets. It requires for its proper 

 growth a clear stream of shallow water, not more than 

 ail inch and a half in depth, running over clear sand 

 and gravel. Deep and still water, especially if the 

 bottom be muddy, is unfavorable. The best situations 

 are in streams near their sources, where the water sel- 

 dom freezes in winter, as here they continue to grow 

 and may be gathered all winter. In planting, the sets 

 are put in rows about eighteen inches apart, and length- 

 wise with the stream. If the depth of water be at 

 first only about an inch, as soon as they begin to grow 

 they will so obstruct its course as soon to increase it 

 to three or four inches above the leaves, a depth re- 

 garded as highly favorable to the growth of the cresses. 

 It is absolutely requisite that the water shall be always 

 running, for when the stream becomes obstructed the 



