77 



3- Agrostis. 



This genus is extremely liable to variation, and accordingly is 

 very difficult to define. The following are the most 

 distinctive features. 



The blade is rough on both surfaces and on margin ; thinner 

 and drier than in ryegrasses, fescues, and dogstails. In 

 these characters it resembles Triticum. Agrostis canina 

 has bristle-like blades. 



The ribs are prominent, acute, or rounded. 



The margins begin to converge very near the base of 

 the blade, giving a characteristic form. 



The base is never eared. 



The ligule is a long, white, thin membrane, hairy on the back. 

 At its shortest, in Agrostis vulgaris, it is almost as long 

 as broad the distinctive feature of this species. 



The blade is rolled. In Agrostis canina, however, the blade is 

 folded ; accordingly, a long liguled Agrostis with folded 

 blades is the species canina. To determine the point, the 

 shoot is cut transversely, 'and the section examined under 

 a lens. 



Summary. 



a. No characteristic colouring matter is developed in the base 



of the sheath. 



b. The blades are rough on margin and surfaces, earless, and 



tapered from the base. 



c. The ligule is long, thin, white, and hairy on the back. 



d. The blades are rolled, but folded in canina. 



