MORPHOLOGY OF THE FLORAL ORGANS 113 



culms produce foliage-branches some or all of which may 

 end in an inflorescence. 



The unit of the inflorescence is the spikelet, which 

 consists of one or more flowers with the subtending floral 

 bracts. The common forms of inflorescence are the spike, 

 the raceme and the panicle. 



143. Kinds of inflorescence. — The spike. — The spike- 

 lets are sessile along an elongated axis. Familiar examples 

 of this form are the members of the tribe Hordeae, as 

 wheat and rye (Figs. 57-62). 



The raceme. — The spikelets are pediceled and borne 

 along an elongated axis. Simple forms of meadow fescue 

 and sheep's fescue show racemes. The individual inflo- 

 rescence of Paspalum is apparently a spike, but really a 

 spike-like raceme. 



The 'panicle. — The spikelets are pediceled and the 

 inflorescence is repeatedly branched. The oat- and blue- 

 grass are familiar examples (Fig. 54). 



Mixed inflorescences. — True spikes, except in the Hor- 

 deae, are rare, as is also the simple raceme. An inflores- 

 cence that is apparently a spike often shows that the 

 spikelets are not sessile but more or less pediceled. Such 

 an inflorescence is properly a spike-hke raceme. Similarly 

 a panicle may be so contracted that the pedicels and short 

 branches are hidden and the inflorescence appears to be 

 a spike, but in precise language should be called a spike- 

 like panicle (Fig. 38). 



The component parts of the inflorescences of the genera Pas- 

 palum and Syntherisma (e.g., crab-grass) are spike-like racemes. 

 The so-caUed spikes or heads of timothy and canary-grass are spike- 

 hke panicles. 



In the genus Andropogon what appears to be a spike consists 

 of a jointed axis, each joint bearing a pair of spikelets, one sessile 



