WATER CRESS. 219 



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, LIN., belongs 

 rather to the department of agriculture. Durham mustard, 

 which is distinguished for its poignancy, though not re- 

 markable for fine color, is said to be made principally from 

 the seeds of the common yellow field-mustard or charlock, 

 Sinapsis arvensis, LIN. 



WATER CRESS (Sisymbrium nasturtium). This is a 

 creeping perennial aquatic plant, very extensively supplied 

 in the English markets. It requires for its proper growth 

 a clear stream of shallow water, not more than an inch and 

 a half in depth, running over clear sand and gravel. Deep 

 and still water, especially if the bottom be muddy, is un- 

 favorable. The best situations are in streams near their 

 sources, where the water seldom 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 lengthwise 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 regard- 

 ed as highly favorable to the growth of the cresses. It is 

 absolutely requisite that the water shall be always run- 

 ning, for when the stream becomes obstructed the plants 

 cease to thrive. After they are cut three times they be- 

 gin to stock, and then the oftener they are cut the better. 

 The cress is regarded as a very wholesome raw salad vege- 

 table, eaten at all seasons, but more especially in winter 

 and spring, when its warm and cordial qualities make it 

 particularly grateful. It is frequently found growing 



