CLASSIFICATION AND INHERITANCE OF SMALL GRAINS 99 



In classifying the cultivated varieties of barleys, the density 

 of the spike, its shape, and the appearance of the awns as well 

 as the color of the seed, have been used. Smooth-awned varie- 

 ties are being produced and it is only a question of time before 

 nearly all awned varieties will be represented by both the rough 

 and smooth-awned forms. 



Species Crosses. Two general results have been obtained 

 from crossing two- and six-rowed varieties. The most frequent 

 result is an intermediate condition in FI in which the lateral florets 

 are awned, but produce little or no fruitfulness. In F 2 a 1 : 2 : 1 

 ratio of six-rowed, intermediate, and two-rowed forms is obtained. 

 Six-rowed and two-rowed forms breed true to these respective 

 characters in later generations. Results of this nature can easily 

 be explained on a single main factor difference (Biffen, 19076; 

 Gaines, 1917). 



The intermedium barleys have generally been considered to 

 be of hybrid origin. A cooperative study carried on at the Min- 

 nesota Experiment Statioa has shown the probable origin of some 

 intermedium forms (Harlan and Hayes 1920). In a cross between 

 Manchuria, a six-rowed barley, and Svanhals, a two-rowed 

 variety, the FI was slightly fruitful and produced intermediate 

 developed awns on the lateral florets. In F 2 a wide range of forms 

 was obtained. The genetic nature of the F 2 plants was deter- 

 mined by growing seed of each in ^3. From the ^3 results it 

 was possible to classify F 2 plants as follows: 



1. Those that bred true for the six-rowed character. 



2. Those that segregated, giving six-rowed, awned intermediate forms 

 with very high fruitfulness of the lateral florets and intermedium forms in 

 a 1:2:1 ratio. 



3. Intermedium forms that bred true, giving few or no awns on lateral 

 florets and producing approximately 50 per cent, of barren lateral florets. 



4. Those that gave all forms as in F?. 



5. Those that produced intermediates and two-rowed types. 



6. Those that produced six-rowed, awned intermediates with little or no 

 fruitfulness in the lateral florets and two-rowed forms in a 1:2:1 ratio. 



7. Those that bred true for the two-rowed condition. 



Results were accurately explained by considering the Manchu- 

 ria parent to contain two factors, one for six-rowed and one for 

 intermedium, which was hypostatic to the six-rowed factor. It 



