The ribbing on the upper surface of the blade is 

 very different from that of red sheathed grasses (rye- 

 grasses and fescue). The difference may be tabulated 

 thus : 



Slender foxtail \ however, has the ribs rounded or 

 acute, like the ryegrasses. 



The nature of the ribbing is best observed when 

 the blade is cut across by a sharp knife, and the 

 section examined by a lens. Without cutting, the 

 height of the ribs may be approximately estimated. 

 This is done by holding the blade up to the light : 

 the degree of contrast between the thin furrows and 

 the thick ribs evidently gives a fair idea of the relative 

 thickness of the parts. 



Summary : 



a. Black or violet sheath. 



b. Ribs low, and flat. 



c. Blade dark green in colour. 



YORKSHIRE FOG. 



Select from the grass pulled up, those i. 4 . 

 shoots which have white sheaths with red 

 veins. The grass is hairy. 



Remove the white sheath, and hold it up to the x. 3 

 light in order to see more distinctly the red veins in 

 the white ground. Observe also the well-marked 

 keel on sheath and blade. 

 B 



