XXVI GRASSES OF BRITAIN. 



AIR A. — Spikelets of two florets. Glumes nearly of equal lengths. 

 Lowermost floret sessile. Outer palea with very indistinct ribs or 

 altogether wanting. Six species, A. ccespifosa^ A. Jlexuosa, A. al- 

 pina, A. caryophyllea, A. -pracox^ A. canescens. 



FES TUG A. — Florets awned from the very summit Leaves of 

 the root very narrow. Four species, F, bromaides, F. uniglumis, 

 F. duriuscula^ F. ovina. 



BUCETUM. — Florets membranous at the summit. Awn when 

 present arising from beneath the summit. Leaves of the root broad 

 and flat. Ligule of upper sheath very small. Four species, B. 

 loliaceum, B. praiense^ B. elatius, B. giganteum. 



BROMUS. — Florets awned from a little beneath the summit. 

 Ligule of upper sheath prominent. Styles arising, generally, from 

 below the summit of the ovarium. Spikelets of not less than five 

 florets. Twelve species, B. maximus, B. mollis, B. racemosus^ B. 

 secalinus, B. commutatus, B. arvensls^ B. patulus^ B. squarrosus^ B. 

 sterilis, B. diandrus, B. erectus, B. asper. 



DAGTYLIS. — ^Panicle tufted. Spikelets of not more than four 

 florets. Florets with a minute awn from a little below the summit. 

 One species, D. glomerata. 



CYNOSURUS. — Spikelets with a pectinated involucre. Florets 

 tipped with a rough awn. Two species, C cristatus, C. echinatus. 



HORDEUM. — Spikelets arranged in threes on each tooth of the 

 rachis. Glumes terminating in bristly awns. Four species, H. 

 murinum, H. pratense, 11. maritimum, H. sylvaticum. 



ELYMUS. — Spikelets arranged in pairs on each side of the ra- 

 chis. Glumes two, situated parallel to each other. Two species, 

 E. arenariusj E. geniculatus. 



TRITICUM. — Spikelets arranged singly on each side of the ra- 



