en. vn] Botanical Description of Species 57 



very high, rough, and acute ridges which are equal, and -contrast 

 greatly with the thin transparent tissue between. This trans- 

 parent tissue consists of longitudinal rows of thin-walled motor 

 cells. There is no mid-rib, and in dry weather the blade rolls up 

 as the motor cells lose water and allow the ridges to come together. 

 There are no auricles ; the ligule is long and acute. 



Flowers usually in July; culms 1J to 4 feet high. Panicle 

 large and graceful at first slightly drooping later erect and 

 spreading; spikelets numerous, 2-3 flowered, silvery-grey or 

 purplish. 



Fig. 38. A large dense tuft of Aira ccespitosa. 



"Seeds" about 2-5 mm. long; outer palea membranous, white, 



and ragged at its apex, and bearing a fine, almost straight basal 



(or almost basal) awn seldom exceeding its own length. Rachilla 



relatively long, and bearing long white spreading hairs. There is 



also a basal tuft of white silky hairs. Colour variable. (Fig. 40.) 



Aira flexuosa, L. (Wavy Hair-grass.) (Fig. 42.) 



A perennial, with narrow leaves having their edges tightly 



rolled inwards, making them almost solid. Ligule prominent, 



broader than the base of the leaf. Flowers in July ; culms from 



