GRASSES OP IOWA. 



43 



Fig. 33. Stomata of grasses, a, wheat; b, Panicum crus-galU; c, Bromusinermis; d, 

 Poa pratenaU; chl, chlorophyll grains; 0, guirdian cells; I, leucoplastids; r, rift; n, 

 nucleus; n', nucleolus. (King.) 



Fig. 33. Stomata of maize leaf, b, bulliform cells, upper surface; ep, epidermal 

 cells with irregular walls; ato, stoma. (Combs.) 



