STRUCTURE OF WHEAT 



29 



af that 

 ar\' in 

 promi- 

 of the 



54, Leaves. — There are four parts of the wheat le 

 should be distinguished : (i) the blade, which may v 

 length and widtn, in shape, in smoothness, and in the 

 nence of its veins ; (2) the sheath, which, as in all plants 

 family, clasps the stem tightly and 

 is split down the side ODposite the 

 blade ; varies in growing plant from 

 green to purple ; (3) the ligule, a 

 thin, transparent tissue borne at 

 the juncture of the blade and 

 sheath and clasping the culm, var}-- 

 ing in length from .07 to .1 of an 

 inch (1.7 to 2.5 mm.^); and (4) 

 the leaf auricle, thin projections 

 of tissue, outgro^\ths from the base 

 of the leaf blade var}-ing in color 

 and hairiness. 



55. Tillering. — Inasmuch as 

 buds form in the axis of the leaves, 

 by covering with earth, both roots 

 and ciilms (branches) will form at 

 any node upon the culm. Ordi- 

 narily, however, branches form only 

 at the lower nodes. The number 

 of branches which can form from 

 a single culm is necessarily lim- 

 ited, but each branch may produce a limited number of 

 branches and these branches in turn other branches, so that 

 under favorable conditions several dozen culms and conse- 

 quently spikes may be produced from a single seed This is 

 kno'\^'n as tillering and is one of nature's methods of giving the 

 plant power to adapt itself to its environment. Under ordinar}- 

 field conditions only a comparatively few culms form, but 



1 The Description of Wheat Varieties. By Carl S. ScofielA U. S. DepL of 

 Agr., Bureau of Plant Ind. Bui. 47, p. 12. 



A wheat leaf, showing I, blade, 2, 

 sheath, 3, ligule, and 4, auricle. 

 (About natural size.) 



