132 A TEXT-BOOK OF GRASSES 



In genera with many-flowered spikelets the rachilla is of 

 course elongated, while in 1-flowered spikelets it is reduced 

 so that the floret seems to be terminal. It often extends 

 beyond the insertion of the upper floret in many-flowered 

 spikelets but is usually hidden by the upper lemmas. In 

 1-flowered spikelets the rachilla may extend beyond the 

 base of the floret. It then appears as a slender sometimes 

 plumose bristle or stalk pressed against the palea. This 

 extension of the rachilla sometimes bears a rudimentary 

 second floret. The first internode of the rachilla above 

 the glumes is sometimes elongated, forming a stipe to the 

 floret. This stipe may be developed into a sharp-pointed 

 callus, which at maturity aids in seed-dispersal (Stipa, 

 Aristida). Usually the intemodes of the rachilla between 

 the florets are short, the florets being closely imbricated; 

 but, occasionally, they are elongated, the florets being 

 rather distant, as in Senites. 



A peculiar jointing of the rachilla is to be observed in Festuca 

 subuliflora Scribn. in which there is an articulation midway between 

 the distant florets. This is probably due to "a downward elongation 

 of the callus, surrounding and becoming grown to the rachilla, 

 which has hkewise become elongated so that the joint is still at the 

 base of the callus." * 



♦Piper, Contr. U.S. Nat. Herb. 10:36. 1906. 



J 



