126 A TEXT-BOOK OF GRASSES 



before (Par. 152). The sterile lemma of Andropogonese, 

 also below the perfect floret as in Panicese, is membrana- 

 ceous, thinner than the glumes, often very delicate. In 

 the tribe Phalarideae, there are usually 2 -sterile florets at 

 the base of the terminal fertile floret (Fig. 34). These 

 lateral florets may be empty (Phalaris, Anthoxanthum) 

 or staminate (Savastana). 



156. The awns are bristle-like continuations of the 

 nerves of the glumes or lemmas. Awns involve vascular 

 tissue while hairs of various kinds (trichomes) involve 

 only epidermal tissue. The commonest position for the 

 awn is terminal as in Festuca, where the midnerve is 

 extended as a bristle. Often the apex of the lemma is 

 cleft and the awn arises from between the lobes or teeth. 

 Occasionally the 2 teeth thus formed are also awned. 

 Sometimes the lateral nerves of the lemma extend into 

 teeth or awns (Tridens). 



In the cases mentioned, the central a^vn is terminal. 

 Sometimes the awn arises below the apex of the lemma 

 even nearly at the base, in which case it is said to be dorsal. 

 When the awn is dorsal, the lemma shows no midnerve 

 above the point of attachment of the awn or rather above 

 the point where the midnerve separates from the tissue 

 of the lemmas, thus forming an awn (Fig. 45). The awns 

 of Aristida (Fig. 35) are usually trifid, with divergent 

 often much-elongated branches (as much as 4 inches long 

 in a South American species). In Pappophorum the 

 lemma is divided at the summit into many awns. In 

 other genera the awns are hooked, or bent, or variously 

 divided, sometimes smooth, but usually scabrous, some- 

 times plumose. In several genera the awn is jointed at 

 the base and deciduous, as in Oryzopsis, Nassella, Pipto- 

 chsetium. 



