SEED-BEARING PLANTS 



493 



the plant families. Here belong the " grains " (wheat, rice, 

 oats, barley, rye, corn, and others) which furnish the most 

 important vegetable foods of the entire human race. The 

 commercial grains have been cultivated so long by man 



FIG. 377. Water plantain (Alisma Plantago-aquatica) . 



that their origin is shrouded in mystery, antedating, as it 

 does, the dawn of written history. Except the bamboos, 

 which are shrubs or trees, the grasses are all herbaceous.' 



The chief characteristics of the family are that the fruit 

 is always a grain or caryopsis. 1 The seed invariably con- 



1 A one-seeded, seed-like fruit, with the wall of the ovary (pericarp) 

 united closely (adnatc) to the seed within. 



