LESSON V 

 SESSILE SPIKELETS IN TWO-SIDED SPIKES 



Returning 



Fig. 25. A, part of a 

 spike of Agropy- 

 ron repens; B, 

 part of rachis 

 seen from the 

 edge, all but 

 two spikelets re- 

 moved. 



again to the spikelet of Bromus 

 secalinus (Fig. 11), we shall strike 

 out in another direction. Differ- 

 entiation among living beings does 

 not follow a line, but radiates like 

 waves following the falling of a peb- 

 ble in the water, or rather like waves 

 of sound, in all directions. Hence we 

 can not follow an unbroken line in 

 studying the increasing complexity 

 of the inflorescence of grasses. We 

 can only return to the center and 

 start out on another line. Compare 

 Fig. 10, A and B, with C, and with 

 Fig. 25 (couch-grass or quack-grass, 

 Agropyron repens). A raceme is a 

 panicle reduced to its lowest terms. 

 Eliminating the pedicels of the spike- 

 lets of a raceme we have a spike, the 

 spikelets set directly upon the rachis. 

 In such an inflorescence the rachis 

 is usually more or less thickened. In 

 Fig. 25, A, part of a spike is shown 

 from the flat side of the spikelet. 

 The rachis is jointed and a spikelet is 

 34 



