112. THE STRUCTURE OF ECONOMIC PLANTS 



while the southern ones frequently attain the maximum noted 

 above. The main stem axis is sometimes unbranched, except for 

 lateral carpellate inflorescences or "ears" which are borne on short 

 branches; but tillers, suckers, or lateral branches may arise from 

 buds located in the axils of the lower leaves. The latter occa- 

 sionally develop as ears or they may form vegetative stems which 

 in turn develop adventitious roots and produce inflorescences. 



Fig. 41 . The mature root system of corn showing its lateral and vertical spread. 

 (After Weaver, Root Development of Field Crops, McGraw-Hill Book Co.) 



The stem is solid with the characteristic jointed appearance of all 

 grasses, and the internodes are alternately furrowed just above the 

 node on the side next to the leaf blade. This furrowing is related 

 to the formation of axillary buds, and, consequently, is more pro- 

 nounced in the internodes above each ear than in the upper inter- 

 nodes where the buds are not well developed. 



The leaves are alternate and two-ranked as in other grasses. 

 Each leaf, except the scutellum and coleoptile, consists of a basal 

 sheath, ligule, and blade. The sheath surrounds the internode 



