INTR O D UCTION 1 5 



Agricultural grasses are either annuals or perennials. 



The annuals are mostly grown as cereals in some part 

 of the world at least, but several are grown in America 

 primarily as forage, such as millets and sorghums. 



The perennials may be distinguished as bunch grasses, 

 like orchard-grass and timothy, and creeping grasses, 

 like Kentucky blue-grass and Bermuda. In the former 

 the new shoots are intravaginal; that is, the new shoots 

 do not break through the lowest sheath but grow erect 

 within it; in the creeping grasses the shoots are extra- 

 vaginal; that is, they pierce the lowest sheath and for 

 a longer or shorter distance develop as rhizomes below 

 ground, or stolons above ground. In a few grasses, like 

 various-leaved fescue, both types of shoots are formed. 



The roots of all grasses are very slender and but little 

 branched. Even in perennial grasses the roots usually 

 live but one season and then new ones are formed. 



To possess high agricultural value, a grass must be 

 palatable and healthful ; it must yield well ; and above 

 all, it must have good seed habits, so that the seed can 

 be harvested cheaply. Even in the best of the perennial 

 grasses the seed is relatively inferior in viability, as com- 

 pared with other crop plants. 



9. Legumes. Legumes or pulses are distinguished 

 botanically by having the leaves alternate, with stipules 

 and mostly compound ; flowers usually papilionaceous 

 that is, like a pea flower ; pistil simple, becoming in fruit 

 a legume ; embryo usually completely filling the seed. 



Biologically, most leguminous plants are remarkable 

 for their ability to use free atmospheric nitrogen, by the 

 aid of certain bacteria that form nodules on the roots. 



Most of the cultivated legumes thrive best in soil con- 

 taining a high content of lime, but others, like trefoil and 



