24 FIRST BOOK OF GRASSES 



staminate or neuter. In spikelets like those of Figs. 

 11-14, with several to many florets, the uppermost 

 florets are commonly sterile (not perfecting seed), 

 though they are like the fertile florets in appearance 

 and have rudimentary stamens and pistils. In some 

 grasses the sterile florets are very different from the 

 fertile ones and may be borne above or below them 

 on the rachilla. The position of sterile florets in the 

 spikelet is the same in large series of related grasses; 

 hence it is of great importance in classifying genera. 

 The type of modification of the sterile floret is also 

 uniform within a genus, and generally in related 

 genera. It conmionly consists of a lemma without a 

 palea, but there may be a rudimentary or even a 

 well-developed palea. 



These types of modification will be brought out 

 and illustrated in the succeeding lessons. 



SUMMARY 



All spikelets are built on the simple plan of 2- 

 ranked florets with a pair of glumes at the base. 

 The spikelet as a whole and each of its organs is 

 subject to modification. The palea and one or both 

 glumes may be suppressed; the lemma may be re- 

 duced but is never suppressed. The position and 

 type of modification of sterile florets are of impor- 

 tance in classification. 



The parts of a spikelet, however complex, are 

 recognizable as rachilla, glumes, lemma, or palea. 



