78 FIRST BOOK OF GRASSES 



tional one (in some older works it is called the acces- 

 sory valve or glume) or is entirely suppressed. The 

 genera differ chiefly in the arrangement of the spike- 

 lets hi the inflorescence. In a few genera some of the 

 panicle branches are without spikelets and are 

 transformed into bristles or burs. 



REVIEW 



Collect the inflorescence of broom-corn millet, old witch-grass, 

 or of as many species of Panicum as are available, and dissect 

 the spikelets. Collect heads of barnyard-grass and compare the 

 spikelets with those of Panicum. Compare the spine-like hairs 

 with those of Nazia, Fig. 54. 



Collect the inflorescence of crab-grass and of any species of 

 Paspalum available; note the arrangement of spikelets and com- 

 pare the form and texture of the fruit (fertile floret) with that of 

 Panicum. 



Collect heads of common millet or of yellow or green foxtail. 

 Remove enough branches from the axis to show clearly the form 

 and arrangement of the few remaining. 



If available, examine a sand-bur, splitting the bur with a 

 sharp knife. 



