36 



FIRST BOOK OF GRASSES 



main in the spike and the ripened grain is thrashed 

 from them. This persistence of the lemma and 

 palea has been fixed by selection in cultivation. In 

 the closely related emmer {Triticum dicoccum) the 



rachis breaks at the joints, each 

 joint remaining attached to its 

 spikelet. 



Compare Fig. 27 {Lolium multi- 

 florum) with Fig. 25. Note that in 

 Fig. 25 the spikelets are borne 

 flat side against the rachis, while 

 in Fig. 27 they stand with their 

 edges against the rachis. The 

 rachis itself is of the same type as 

 that in Fig. 25. The diagram- 

 matic rachis with two spikelets 

 seen edgewise (Fig. 25, B) is shown 

 from the same position as is Fig. 

 27. In this, as in Agropyron, the 

 rachis is continuous (not disartic- 

 ulating) and the florets fall. If 

 we separate a spikelet from the 

 rachis we find that the first glume 

 (the one that would be against the rachis) is sup- 

 pressed, the first floret lying directly against the 

 rachis. In the single spikelet borne at the summit 

 of the rachis the first glume is developed and is 

 about as large as the second. When but one glume 

 is present, we know which glume it is and which is 

 suppressed by the position of the first floret, which 



Fig. 27. Part of a spike 

 of Lolium multiflorum. 



