PAIRED SPIKELETS 



83 



in the spathes. The racemes may be sohtary (that 

 is, one to a branch, as shown) or two to several, 

 digitate, on a single branch. In some species the 

 sterile spikelet is suppressed, only the pedicel being 

 developed. In a few species of Andropogon the 

 racemes are in leafless panicles, 

 as in Erianthus, but the pedi- 

 celed spikelets are sterile and 

 awnless. 



Examine Fig. 76, A (Mani- 

 suris cylindrica) , and compare 

 it with 73, A. In Holcus and 

 Erianthus the rachis joint and 

 the pedicel of the second spike- 

 let are about equal in thick- 

 ness. In Fig. 75 the rachis 

 joint is stouter than the pedi- 

 cel. In Manisuris the rachis 

 joint is greatly thickened and 

 hollowed out below on the inner 

 face. (See Fig. 28, p. 37, for an 

 earlier example of a thickened 

 rachis.) The pedicel of the ster- 

 ile spikelet is also thickened, 

 but much less so, and the two 

 lie close together (instead of 

 spread apart, as in Figs. 73 to 75) and entirely cover 

 the second-glume side of the spikelet which fits into 

 the cavity formed by the rachis joint and pedicel. 

 Fig. 76, C, shows the inner faces of the rachis joint 



Fig. 76, A , single joint of 

 raceme of Manisuris cy- 

 lindnca; B, another view 

 of two joints; C, inner face 

 of rachis joint and pedi- 

 cel, spikelet removed; D, 

 part of cylindrical many- 

 jointed raceme. 



