THE WHEAT PLANT 



regular intervals, are pairs of cells, the upper one oval, the lower one 

 broader and curved (Fig. 50) ; trichomes when present arise from the 



oval cells. 



The cells of the inner epidermis of 

 the sheath are thin - walled. Inter- 

 calated in the rows lying between the 

 points opposite the vascular strands, 

 especially near the upper part of the 

 sheath, are short hairs, the tips of 

 which are directed forwards (Fig. 51). 

 A few stomata of a simpler pattern 

 than those of the blade are found in 

 this region of the inner epidermis ; 

 these communicate with larger lysigen- 

 ous lacunae in the mesophyll. 



(b) The Parenchyma of the Leaf. 

 FIG. so.-Outer epidermis of the base of Th parenchyma o f the blade o f the 

 a young leaf-sheath ( x 210). J . 



foliage leaf consists chiefly of thin- 



walled assimilating tissue, containing lenticular chloroplasts 4-5-6 p in 

 diameter. Just within both the upper and lower epidermis the cells are 



FIG. 51. Inner epider- 

 mis of the leaf-sheath 

 f x 5). 



FIG. 52. A, Outer epidermis of the leaf- 

 sheath ; B, transverse section of the same 

 ( x 210). 



somewhat elongated and arranged in a more or less regular manner, 

 with their long axes at right angles to the surfaces of the lamina, both 

 layers suggesting a resemblance to the palisade parenchyma of a leaf of a 



