MORPHOLOGY OF THE FLORAL ORGANS 125 



awns, as in some species of Chlorideae, is to be recognized 

 by its position on the rachilla. In canary-grass (Phalaris 

 canariensis L.) there are 2 minute bracts at the base of the 

 fertile lemma. These are greatly reduced lemmas. The 

 indurated lemma of Stipa and Aristida is peculiar in that 

 it assumes a cylindrical form and extends downward into 

 a hard, sharp-pointed callus (Figs. 35, 36). At maturity 

 the fruits, by means of this sharp point and by the 

 hygroscopic awns at the apex, are able to bury themselves 

 in the soil. Certain genera of Andropogonese (Hetero- 

 pogon, Chrysopogon) produce fruits similar in general 

 appearance to those of Stipa, but in the former the fruit 

 is developed from a spikelet instead of from a floret. 



In Heteropogon and other genera of Andropogonese with stout 

 awns, the first glume is indurated, cylindrical and sharp-pointed at 

 base as in the lemma in Stipa. Within this are the second glume, the 

 sterile lemma and the fertile lemma, all thin and hyaline, the latter 

 bearing the long stout awn. 



155. Sterile florets and sterile lemmas. — Sterile florets 

 are those which differ from the perfect florets of the spike- 

 let in which they are found in lacking pistils. They may 

 also lack stamens, and consist of a lemma and palea, or 

 the palea also may be lacking. The lemma of such a 

 floret is called a sterile lemma. If a lower floret lacks 

 stamens, then the lemma is the same as the third empty 

 glume of some authors, when they refer to bracts above 

 the first pair. In many genera of the series Poaoidese the 

 upper florets are reduced to sterile florets. In Melica 

 there may be 2 or 3 sterile lemmas successively convolute 

 one within another. In most of the genera of Panicoidese 

 there is a sterile floret below a terminal perfect one. The 

 sterile floret of Panicum and its allies has been mentioned 



