120 A TEXT-BOOK OF GRASSES 



fications will be discussed in detail later. Unisexual 

 spikelets have been mentioned under Par. 144. 



150. Sterile spikelets. — Sterile spikelets are those 

 which differ from the spikelets with which they are 

 associated, in lacking sexual organs. For convenience 

 the term is sometimes made to include spikelets that con- 

 tain stamens, when such spikelets are the equivalents of the 

 sterile ones. In Andropogon the spikelets are in pairs, a 

 sessile fertile one and a second pediceled one, which 

 in different species may be staminate, empty or reduced 

 to the pedicel (Fig. 16). This second or pediceled spike- 

 let is generally referred to as the sterile spikelet. In some 

 genera in other tribes sterile spikelets occur, usually in a 

 definite relation to the fertile ones. These sterile spike- 

 lets are prominent in Achyrodes and Cynosurus. In 

 Hordeum the spikelets are in clusters of 3, but usually 

 the 2 lateral are sterile. In Phalaris paradoxa the spike- 

 lets are in groups of 7 of which 6 are sterile. Sterile spike- 

 lets (when lacking stamens) are sometimes called neuter 

 or neutral spikelets. Staminate spikelets, except those 

 referred to above which have a definite position and are 

 the equivalents of neuter spikelets, should not be called 

 sterile spikelets. 



151. The pedicel is the stalk of the individual spikelet 

 and represents the ultimate branching of the inflorescence. 

 If the pedicel is so short that it is not evident the spike- 

 let is said to be sessile. On the other hand the pedicels 

 may be elongated and extremely slender as in Orthoclada. 

 Sometimes they are slender and nodding, so that the 

 spikelets vibrate or tremble in the breeze, as in Briza 

 media, the quaking-grass. The pedicel may be jointed 

 below the spikelet, in which case the spikelet disarticu- 

 lates from the pedicel at maturity. This is true of most of 



