148 THE STRUCTURE OF ECONOMIC PLANTS 



usually sterile and imperfect, so that only two or three kernels 

 are matured except in some of the club wheats, in which the spike- 

 let may contain five or more. On the average, each spikelet has 

 four flowers and produces two mature grains. 



Each bract, aside from the two sterile basal glumes, is known as a 

 lemma and bears a flower in its axis. The lemma may be beardless. 



: — ra 



roc 



B 



Fig. 61. A, the rachis of the inflorescence showing the rachilla, ra; B, a. single spikelet; 

 C, a flower with the lemma removed and the palea drawn back to expose the enclosed floral 

 parts: «, awn; rf«, anther; ^.glumes; /w, lemmas ; /o, lodicules ; ety, ovary; />, palea; rac, 

 rachis; stg, stigmas. (^A, redrawn from Percival, The Wheat Plant, Duckworth and Co.; 

 B and C, redrawn from Robbins, Botany of Crop Plants, P. Blakiston's Son and Co.) 



although few wheats are strictly so; or bearded with a terminal 

 awn that tapers from base to tip and is sub-triangular in transection. 

 Its epidermis like that of the glume is comprised of elongated cells 

 with sinuous walls, and oval ones that are often papillate. The 

 fine pointed, thick-walled hairs are directed toward the apex of the 

 awn and give it a scabrous character. Stomata occur in rows on the 

 outer face of the awn; and underlying them are zones of chloren- 

 chyma, while the angles are reinforced by bands of mechanical 



