SESSILE SPIKELETS IN ONE-SIDED SPIKES 



57 



(page 23). In Melica (Fig. 19) we had an example 

 of such sterile florets, and in Chloris we have another. 

 In each case, the sterile lemmas if spread out show 

 their derivation from the ordinary fertile lemmas. 



In grama grass, Bouteloua 

 (Figs. 50 and 51), is found 

 the greatest specialization 

 of the sterile floret. It 

 is often more prominent 

 than the fertile floret and 

 so modified that its deriva- 

 tion is not always obvious. 

 The pattern of its lemma, 

 however, is like that of 

 the fertile one, 3-nerved, 

 the nerves extending into 

 awns (Figs. 50, C and 51, C.) 

 The internerves are com- 

 monly broadened and re- 

 duced (as in Fig. 51, C), or 

 even suppressed. There is 

 usually a single such floret, 

 but in some species there are 

 two, or even three. A second 

 sterile lemma when present 

 may have a single awn or be 

 awnless, or even nerveless (Fig. 51, D). In a few 

 species the sterile floret sometimes incloses a palea 

 and stamens. Note that in Bouteloua the spikes are 

 not digijiate, as in the foregoing genera, but are 



Fig. 50. A, spikelet of Boute- 

 loua curtipendula; B, fertile 

 lemma spread out; C, sterile 

 lemma spread out; D, in- 

 florescence. 



