SELECTION OF SEED; FARM CROPS. 127 



for starchy food, the tomato and egg-plant, useful for 

 their fruit, and tobacco, a plant of great commercial value, 

 is also very important. Many plants of this family are 

 poisonous, of which " henbane " and deadly " nightshade " 

 are examples ; in fact, the fruit and vine of the potato 

 contain poisonous principles. In point of food value the 

 potato stands next to the cereals. 



The Sweet Potato belongs to the morning-glory fam- 

 ily, and is the chief food-plant belonging to this order. 



The Legume or Clover Family includes a very large 

 number of plants, as herbs, shrubs, and trees. A distin- 

 guishing feature of this order is the formation of seed 

 in a pod or legume. Those in which the seed or grain 

 is used as food, as peas, beans, and lentils, are called 

 " pulse ; " hence this name has been extended to all the 

 food plants of this order. Leguminous crops are called 

 "pulse crops." 



The other plants of this family, useful as hay, green 

 forage, or pasture, are the various clovers, white or Dutch 

 clover, red clover, alsike or Swedish clover, and crimson 

 or scarlet clover, also lucerne or alfalfa, vetches, lupins, 

 serradella, and sanfoin. These plants are among the 

 most valuable of our forage crops. They have strong 

 foraging powers for mineral constituents, and are also 

 able to secure the nitrogen necessary for their growth 

 from the air ; thus they enrich, rather than impoverish, 

 the soil of the most important element, nitrogen. 



The Turnip Family includes among the edible plants, 

 turnips, the various varieties of cabbage, as cauliflower, 

 kale, kohlrabi, mustard, radish, horseradish, and watercress, 

 and the forage plants, swedes and rape. This order also 



