PART II. ECONOMIC PLANTS 

 CHAPTER V 



GRAMINEAE 



ZEA MAYS 



THE grass family includes many important crop plants which are 

 used for forage and as cereals. Among the cereals grown in 

 the United States are: oats, Avena sativa L.; barley, Hordeum 

 vulgareL.; rye, Secale cereale L.; rice, Oryza sativa L.; wheat, 

 Triticum sp.; and corn, Zea Mays L. Sugar cane, Saccharum 

 officinarum L., is also an outstanding economic grass; and there 

 are numerous meadow and range grasses which constitute the 

 chief forage crops. 



GENERAL MORPHOLOGY 



The Root. — Corn is an herbaceous monocotyledon with an 

 annual cycle. The mature plant has an extensive fibrous root 

 system consisting of several whorls of adventitious roots some of 

 which become wide-spread laterals, others deeply penetrating 

 vertical roots. Weaver (14) reports, 



"A lateral spread of 3.5 feet on all sides of the plant is not uncommon 

 even early in its development, and a depth of penetration of 5 to 6 feet 

 is usual. The degree of spreading as well as the depth varies some- 

 what with soil and other conditions, the root system probably reaching 

 its greatest development in deep mellow soils only moderately well 

 supplied with water." (Fig- 41) 



The primary root may persist during the entire life of the plant, 

 although it frequently decays; but it has little functional impor- 

 tance after the establishment of the adventitious root system. 



The Shoot. — The stem of the corn plant varies within a wide 

 range, some of the dwarf varieties being less than x feet tall while 

 certain types of field corn may attain a height of ix to 15 or even 

 lo feet. Northern varieties usually reach a height of 6 to 7 feet. 



III 



