40 



FIRST BOOK OF GRASSES 



floret of the central spikelet is well developed while 

 those of the lateral florets are rudimentary, and that 

 the back of the floret is turned from the rachis with 

 the glumes (bristle-like in this species) at the sides 

 or back, contrary to the arrangement characteristic 



of grass spikelets. The 

 problem of the glumes 

 in Hordeum has not 

 been satisfactorily 

 solved. It appears prob- 

 able that the reduced 

 rachilla joint between 

 the second glume and 

 the floret is twisted 

 and bent inward, bring- 

 ing the glumes at the 

 side or back of the 

 floret. In the culti- 

 vated barley the rachis 

 does not break up, as 

 in the wild species, the 

 continuous rachis having been fixed by selection. 

 The florets fall from the spike in thrashing, or in 

 naked or hull-less barley the grains fall from the 

 lemma and palea, as in wheat. In cultivated 2-rowed 

 barley the lateral spikelets are pediceled and sterile, 

 as in the wild species, but in 4-rowed and 6-rowed 

 barley the lateral spikelets are sessile and fertile, 

 characters fixed by selection. 



The grasses characterized by the spicate in- 



FiG. 30. Joint of spike of Hcrdeum 



nodosum. 



