264 Plant Biology 



process of tanning, the tannic acid combines with the skins of animals 

 to render them soft, pliable, and useful. 



Foods. — Foods may be defined as chemical substances which, when 

 taken into an animal body, supply energy, help build body materials, or 

 regulate metabolic processes. Vitamins are of the latter group and the 

 various types are quite well represented in the plant kingdom. In fact, 

 our chief natural sources of the various types of vitamins depend directly 

 and indirectly on plant materials. 



Of the great varieties of foods, only the following will be considered 

 briefly: cereals, nuts, legumes, vegetables, and fruits. 



The cereals most commonly used are corn, wheat, oats, rice, barley, 

 rye, and buckwheat. Corn (Figs. 58 to 60), which was originally grown 

 principally for food, has become the basis of a large number of com- 

 mercial products such as corn syrup, corn starch, corn oil, dextrine (for 

 pastes), and cellulose for paper pulp and building materials (from stalks 

 and husks). The hulls of oats contribute an important chemical solvent 

 known as furfural, from which plastic materials used in manufacturing 

 phonograph records, etc., are made. 



Nuts are edible kernels protected by shells. Among the more common 

 are birch family (filbert or hazelnut), beech family (chestnut), walnut 

 family (black walnut, butternut, or white walnut, hickory nut, pecan, 

 etc.), myrtle family (Brazil nut), palm family (coconut). 



Among the various legumes used for food are pulse family (garden 

 peas, garden beans (Figs. 55 and 56), lima beans, etc.) 



Among the common vegetables are nightshade family (white potato), 

 morning-glory family (sweet potato), sunflower family (artichoke, let- 

 tuce, etc.), parsley family (celery), goosefoot family (spinach), lily fam- 

 ily (onion, asparagus, etc.), mustard family (cabbage, cauliflower, kohl- 

 rabi, Brussels sprouts, etc.) 



Some of the common fruits are gourd family (pumpkin), nightshade 

 family (tomato, egg plant), rose family (apples, pears, quinces, plums, 

 cherries, raspberries, etc.) 



Beverages. — Coffee (Coffea arahica) is obtained from green, oblong 

 berries which grow on an evergreen plant. The plant grows to a height 

 of 20 feet but usually is pruned to 6 or 8 feet in order to secure uniform 

 flavor and ripeness, as well as to make it easier to harvest. The plants 

 bear when four years of age. The plants produce a great number of 

 white flowers with a jasmine-like fragrance which rivals that of an orange 

 blossom. The flowers produce the green berries, which develop in six 



