ii6 THE STRUCTURE OF ECONOMIC PLANTS 



layer has been reported by Sargant and Robertson (17) as 

 follows : 



"The glands are scattered over the whole surface of the epithelium 

 except where it covers the top of the scutellum." They "differ greatly 

 in size. Some of the smallest are funnel-shaped pits, others shallow 

 slits, and it is very difficult to draw the line between structures which 

 deserve the name of glands and mere depressions or wrinkles." 



B 



colp no 

 - mer reg 



■ -.\-.-.-adv rt 



- scu no 



— coir 



— pri rt 



Fig. 43. Longitudinal diagram of the embryo showing vascular system and meristematic 

 regions: ^, before germination; B, after germination: ^^j; ^^, adventitious root; colp, coleop- 

 tile; colp no, coleoptilar node; coir, coleorhiza; mer reg, meristematic region; pri rt, primary 

 root; scu, scutellum; scu no, scutellar node. (After Avery.) 



Their frequency is variable, but they are more abundant on the 

 upper portion of the abaxial surface and on the wings of the scutel- 

 lum than on the lower portion. 



The primary root is enclosed by the coleorhiza; and the partially 

 disintegrated suspensor, which persists during the maturation of 

 the grain, may be seen in median longisections at its distal end. 

 The coleoptile is cone-shaped, enclosing the embryonic leaves, of 

 which about five develop, and the growing point of the epicotyl. 



