518 



WEED FLORA OF IOWA 



Fig. 395. Chess (Bromus secalinus). Outer epidermis of flowering glume in 



surface view. X 160. 



(After Winton, Conn. Agr. Exp. Sta.) 



Palet. — The flowering glume and palet of chess are very similar 

 in structure, but the outer epidermis of the latter is barbed on the 

 keel, the stiff hairs often reaching 45/* in length. 



Pericarp (F). — The pericarp consists of two layers with rudi- 

 ments of another layer in parts. 1. The Epidermal Cells (ep) are 

 large, elongated-polygonal, and have thin, non-porous walls. 

 2. Mesocarp. As a rule, the cross-cells immediately underlie the 



at— 



Fig. 396. Chess. Transverse section of fruit. F, pericarp consisting of 

 epidermis ep, and cross-cells q ; S, testa ; N, perlsperm ; B, endosperm con- 

 sisting of aleurone layer al, and starch-parenchyma st. X 160. 

 (After Winton, Conn. Agr. Exp. Sta.) 



epidermis, but occasionally traces of the mesocarp are evident. 

 3. Cross-Cells (q). Whether this layer corresponds with the cross- 

 cells of the tube-cells of other grasses, I have been unable to decide. 



