48 CLASSIFICATION ACCORDING TO [CH. 



with 5 — 6 white lines between, if viewed by transmitted 

 light. Wet meadows. 



A. caespitosa cannot easily be mistaken for any other species. 

 Alopecwrua genicvlatus is also a moisture-loving grass with strongly 

 ridged leaves, but the interspaces are far less translucent and the 

 whole habit is different. 



AU the other species of Aira have involute and setaceous leaves, 

 and even A. ecespitosa is apt to roll in its leaves in mountain 

 varieties, but they are easily flattened out, and show the ridges. 



Psamma arenaria, Beauv. (Sea Mat-grass). This is 

 one of the most valuable " sand-binders," its long matted 

 rhizomes holding loose sand together. It is a sea-shore 

 grass, of no use for fodder. It was formerly much used 

 for mats and thatching. Leaves concave, long, narrow, 

 erect, scabrid and glaucous above, and polished below : 

 pungent. Ridges rounded, alternately high and low. 

 Sheath long. Ligule very long and bifid. 



Elymus arenarius, L. (Sand Lyme-grass). Like 

 Psamma, this is a "sand-binder" and of no use for 

 fodder. Leaves concave, and eared at the base of the 

 blade : ears pointed and tend to cross in front. Ligule 

 very short and obtuse. Ridges flattened above, not 

 scabrid. Apex of blade rolled, forming a hard spine. 



Psamma cannot easily be mistaken for the much less common 

 Elymus, as it is not eared, and the ridges and ligule are very 

 different. 



(ii) Leaves not specially rigid and hard, and often thin; 

 glabrous, or shining below. Ridges less evident. 

 * Ligule very short or obsolete; blade firm, but not 

 hard, glabrous or nearly so, and shining below. 

 Sheath often colowed red or yellow at the base. 

 t Sections of sheathed leaves narrow, oblong, owing 

 to compression of shoots. Sheath nearly entire. 



