162 PLANTS AND MAN 



back to this continent by the Irish immigrants to New England 

 in 1719. Being native to high cool regions, potato plants thrive 

 in northern temperate climates; they are commercially valuable 

 crops in Maine, New York, Minnesota, Michigan, Wisconsin 

 and Idaho. In addition to their use as food, potatoes are utilized 

 in the manufacture of starch and alcohol. 



It was the attempt to produce a better potato which started 

 Burbank on his career as a plant breeder. After many fruitless 

 attempts at crossing potato flowers (which usually produce 

 sterile fruit), Burbank by chance discovered that nature did 

 what he had failed to accomplish. In 1 870 he discovered a single 

 potato plant in his truck garden which possessed a seed-ball. He 

 cared for these seeds until spring, then planted them; each grew 

 into a potato plant with different traits, especially in size and 

 quality of tubers. Two plants produced larger whiter potatoes 

 than had ever been grown before. Burbank sold his prize tubers 

 to a seedsman for $125 — a fortune in his eyes at that time, since 

 it enabled him to set out for California and his long dreamed-of 

 work with plant breeding in that fortunate climate. On the other 

 hand these few tubers were the beginning of the race of Burbank 

 potatoes which in a few decades were bringing in millions of 

 dollars to potato growers of the entire world. Today there are 

 over five hundred varieties of potatoes under cultivation. 



Leaves as Food 



Although some food is stored in leaves, there is rarely suffi- 

 cient to give much nutritive value to leaves as articles of human 

 diet. Leaves are eaten chiefly for their mineral and vitamin con- 

 tent. Edible leaves of cultivated plants are found in the Pigweed 

 Family — spinach and chard; the Mustard Family — cabbage, 

 kale, Brussels sprouts, kohlrabi, broccoli and cauliflower; the 

 Parsley Family — parsley; the Composite Family — lettuce; and 

 the Lily Family with onions and their related varieties. 



Chard is the most ancient cultivated member of the beet 

 genus, having been grown as early as 300 B.C. in its native 

 Mediterranean region. At first its importance lay in its storage 

 root, as in the common beet; but selection emphasized the forma- 

 tion of fleshy succulent leaves at the expense of the root. The 



