332 ESSENTIALS OF BOTANY 
The Gourd family furnishes many edible fruits. Of these 
the pumpkin and the summer squashes are varieties of 
the same species, and the large winter squashes belong to 
another species of the genus Cucurbita, probably of Amer- 
ican origin. The watermelon belongs to a genus (Citrul- 
lus) of Asiatic origin. The muskmelons, nutmeg-melons 
and other varieties, and the cucumber belong to another 
genus (Cucumis), and most of our varieties are descended 
from two southern Asiatic species. 
408. Edible Leaves, Stems, and Roots. — Not many 
kinds of food of prime importance consist of the leaves 
or aérial stems of plants. The Lily family yields aspar- 
agus; the Pigweed family, spinach; the Mustard family, 
water-cress, cabbage, cauliflower, and Brussels sprouts ; 
the Parsley family, celery; and the Composite, lettuce and 
globe artichokes (Cynara). 
Since the underground portions of the plant often store 
up much reserve material (Sect. 76), it is evident that 
bulbs, rootstocks, tubers, and roots must often be of 
value as food. Only a few of the most important of these 
are here mentioned. The Lily family yields onions; the 
Yam family, yams; the Pigweed family, beets; the Mus- 
tard family, turnips and radishes; the Parsley family, 
carrots and parsnips; the Morning-glory family, sweet 
potatoes; the Nightshade family, potatoes; and the Com- 
posite, salsify and Jerusalem artichokes (Helianthus). 
The potato crop is so important that a few words may 
here be said, about it. The annual yield for the United 
States is usually over 200,000,000 bushels. Introduced 
into cultivation from Peru, potatoes soon became one of 
the principal foods of the cooler parts of the world. They 
are particularly well suited for cultivation in regions where 
