IOWA ACADEMY OF SCIENCES 



207 



Between the bundles and the upper or inner epidermis is the 

 pith, made up of colorless parenchyma; this makes up the 

 body of the keel. 



The blade proper, in surface section of the superior or inner 

 face (lower figure, Plate XI), shows epidermal cells irregularly 

 rectangular in shape, with a wavy or dove-tailed outline. 

 Between the ends of the cells is often a small, spur-shaped pro- 

 tuberance or hair. The long stomata are located between the 

 ends of the cells of every third or fourth row. Their regu- 

 larity in shape and arrangement is more or less interfered with 

 along the bulliform areas. In addition to the stomata, which are 

 moisture regulators serving also in the exchange of gases, rifts 

 from which water exudes occur at the apex of growing corn 

 leaves. 



The bulliform areas are composed of from three to seven 

 rows of polygonal cells with thin walls, are arranged longitu- 

 dinally with the leaf, and are occasionally interrupted by or 

 grade into the exserted cells about the base of the large hairs. 

 These areas are usually about fourteen rows of epidermal 

 cells from each other, and are located alternately with the 

 veinlets. The epidermis of the lower or outer face is much 

 the same as above, except that bulliform cells, hairs, and spur- 

 like hairs or tubercles, are wanting and the walls are thicker. 



Fig. 13 

 Cross section of leaf blade showing: 6, normal bulliform area with t, short spur- 

 llke hair; ep., epidermal cells of upper surface; c. p. s.. cholorophyll parenchyma 

 sheath of mestome bundle embedded in the mesophyll; m., mesophyll; i. s., inter- 

 cellular space; 8, stoma. 



