78 BOTANY OF CROP PLANTS 



The upper portion of the leaf may therefore be removed 

 without permanent injury to the plant. This is well shown 

 in the rapid recovery of the leaves of lawn grass after mowing, 

 and of pasture grasses after grazing. 



Scales and Bracts. — Reduced leaves in the form of scales 

 and bracts occur in grasses. Such reduced leaves are termed 

 "scales" when they appear lower on the stem than the 

 foliage leaves, and "bracts" when higher. For example, 

 the reduced leaves at tillering nodes are "scales" (Fig. 

 27), while the reduced leaves (glumes) in the inflorescence 

 are "bracts" (Fig. 28). Scales and bracts seldom possess 

 chlorophyll (green coloring material in plants), and, hence, 

 are incapable of carrying on synthesis of carbohydrates. 

 The scales and bracts in grasses have the same one-half 

 spiral arrangement as the foliage leaves and although they 

 may be very close together on the axis, careful observation 

 shows them to have this typical arrangement of all grass 

 leaves. 



Ligule. — ^At the junction of the sheath and blade is a 

 membranous or cartilaginous ring or fringe, the ligule (Fig. 

 26). It is next to the culm, and varies id size, shape, and 

 hairiness in different species of grasses. The ligule is 

 sometimes absent. 



Auricle (Fig. 26). — This is a more or less pointed, thin, 

 ear-like structure projecting from the leaf edge at the junc- 

 tion of sheath and blade. It often clasps the stem but 

 may be more or less twisted and bent away from it. It 

 varies greatly in size and shape. In the tribe Hordeae, 

 the auricles are characteristic. They are entirely absent 

 in some species. 



Inflorescence. — ^The grass inflorescence (flower cluster) 

 consists of a number of groups of flowers, each group being 

 called a spikelet. The spikelet is, in fact, the unit of the 



