ON THE CHALK 311 



species grows from six inches to a foot in height, and flowers from 

 May to July. It is moderately common in the open spaces and on 

 the banks of some calcareous districts. 



Although a great variety of Grasses (order Gramineoi) are to be 

 found on calcareous soils, there are two common species which are 

 almost exclusively confined to dry, chalky pastures. One is the 

 Downy Oat Grass {Avena piihescens), which flowers in June and 

 July. It has a creeping stem, and grows from one to two feet high. 

 The radical leaves are short, haixy, with sharply-pointed ligules, 

 and terminate abrujitly in a sharp point. The flowers are arranged 

 in a nearly simple panicle, with erect spikelets of five or six flowers. 

 The glumes are nearly equal, the inner one with three ribs. The 

 flo\\ering glume is divided at the tip, and provided with a long, 

 bent, twisted bristle. 



The other, numbered 7 on Plate VIII, is the Yellow Oat Gi'ass 

 (A. flavescens), which grows to about the same height, and flowers 

 at the same time. In this species the radical leaves are hairy, and 

 also terminate suddenly in a sharp point. The panicle is much 

 branched, with erect spikelets of five or six flowers. In this one, 

 too, the inner glumes have three ribs, but it may be distinguished 

 from the last by the two terminal bristles of the inner scales, and 

 by the blunt Hgules (appendages at the base) of the sheathing leaves. 



