DIVERSELY SPECIALIZED SPIKELETS 67 



anomalous in that it has three nerves. Throughout 

 the grasses the palea has two nerves, rarely sup- 

 pressed, as in Agrostis, where the palea itself is much 

 reduced, or so close together as to be merged into one, 

 but in no case are more than two nerves known. The 

 problem presented by this spikelet has not been sat- 

 isfactorily solved. It is possible that the two organs 

 are, respectively, the second glume and the lemma, 

 the first glume and the palea being suppressed. In 

 the pistillate spikelet the palea is 2-nerved. In the 

 perennial wdld rice of the southeastern states, Zizani- 

 opsis miliacea, this 3-nerved organ is present in both 

 the staminate and pistillate spikelets, and in another 

 related genus, Luziola, both bracts of the spikelets 

 are several to many nerved. 



SUMMARY 



In the highly specialized spikelets studied in this 

 lesson the various organs are identified (1) by their 

 position, bearing in mind that the bracts of a spikelet 

 are 2-ranked and alternate on the rachilla, and 

 (2) by their resemblance to corresponding organs in 

 allied grasses. 



REVIEW 



Hilaria, Nazia, and iEgopogon are found only in the South- 

 west, but the other grasses studied in this lesson are widespread. 

 In any region in the United States will be found one or more of 

 them. Collect any that are available, examine the inflorescence, 

 distinguish the spikelets, and identify their parts. 



If in a species of Phalaris but one sterile floret is found below 

 the perfect one, how can you tell which of the pair is suppressed? 



