98 BREEDING CROP PLANTS 



gous forms are less heavily awned than the false wild and have 

 the fatua type of callus only on the lower grain. Considerable 

 difference of opinion is held regarding the cause of the production 

 of false wild oats. Whether they originate as a loss mutation 

 or through hybridization or both is not yet determined. Some 

 evidence for hybridization and some for mutation has been 

 obtained. 



CLASSIFICATION AND INHERITANCE IN BARLEY 



Students of barley classification have frequently used density 

 and sterility of the lateral florets as chief means of separating 

 the larger cultivated groups. While density is quite a stable 

 character, there are gradations in the length of the internode 

 from the very lax to the very dense spikes without any clear-cut 

 differentiation between the mid-dense and mid-lax groups. 

 While density is an important character by means of which to 

 differentiate forms, it is not very usable as a chief means of 

 group classification. Harlan (1918) has made an interesting 

 review of barley classification studies and has presented a new 

 grouping in which species are made on the basis of fertility of 

 the lateral florets. The following key is taken from Harlan 's 

 paper : 



All spikelets fertile (six-rowed barley) 



Lemmas of all florets awned or hooded Hordeum vulgare L. 



Lemmas of lateral florets without awns or hoods . . .H. intermedium Kcke. 



Only the central spikelets fertile (two-rowed barley) 



Lateral spikelets consisting of outer glumes, lemma, palea, rachilla, and 

 usually rudiments of sexual organs H. distichon L. 



Lateral spikelets reduced usually to only the outer glumes and rachilla, 

 rarely more than one flowering glume present and never rudiments of 

 sexual organs H. deficiens Steud. 



There are several contrasting characters by means of which 

 variety groups are made. Harlan has used the following to dif- 

 ferentiate the variety groups belonging to each of the four species 

 groups : 



Seeds hulled; seeds naked. 

 Lemmas awned; lemmas hooded. 

 Seeds white, blue, purple; seeds black. 



