73 



Note i. Many hairy grasses have low flat ribs, for 

 example : 

 Avena elatior. Ligule conspicuous, blade thin 



and dry. 

 Triodia. Ligule a hair tuft ; blade with median 



lines like Poa. 

 Triticum. Blade eared, thin and dry. Ligule 



inconspicuous. 



Note 2. The marginal roughness of the blade is im- 

 portant in this group; it is detected by running the 

 margin along the tip of the tongue. Upward rough- 

 ness; marginal teeth directed downwards. Down- 

 ward roughness; marginal teeth directed upwards. 



Group XIV. Ribs High and Prominent, 

 Rounded, or Acute. 



NOTE. The ribs of Agrostis are lowest of all. 



Hairless. 



Extremely hard bladed. Elymus, Psamma, Air a. 

 Ligule very short. 



Elymus arenarius, L. (Sand lyme grass). Blade 

 eared. Ligule very inconspicuous, like that of 

 Triticum. A sandbinder. 



Fig. 3. Eared base of blade ; ligule inconspicuous. 

 Fig. 4. Transverse section of rolled blade, shewing 

 the prominent ribs flattened on the summit 

 (magnified). After Lund. 

 Ligule very long. 



Psamma arenaria, R. & S. (Sand mat grass). Blade 

 earless. Ribs mixed (uniform in Elymus). A sand- 

 binder. 



Fig. I. Earless base of blade and long ligule. 

 Fig. 2. Transverse section of rolled blade, shewing 

 the prominent and mixed ribs (magnified). 

 After Lund. 



Aira caespitosa, L. (Tuftecl hair grass). When held 

 up to the light the spaces between the ribs appear 

 as siioiv-white lines (II. 4). 



Fig. 5. Transverse section of blade, shewing the 

 very high and very acute ribs (magnified). 



