26 BULLETIN 622, U. S. DEPARTMENT OF AGRICULTURE. 



and distichon do not fall clearly into the two groups of their parents. 

 How much the heterozygous character is responsible for the confusion 

 remains to be determined. How broad the interpretation of inter- 

 medium should be is also a matter of doubt. It may be that it should 

 include forms in which the lateral florets are sterile but pointed. 

 This would explain such forms as attervergii Kcke., which most prob- 

 ably are genetically nearer intermedium than distichon, even though 

 the pointing of the glume is a glume character and not one of 

 fertility. 



IDENTIFICATION OF THRASHED MATERIAL. 



Of necessity the keys have been based on spike characters. Fre- 

 quently, however, it is necessary to identify a barley from thrashed 

 kernels alone. This is not always possible, but ordinarily the chance 

 of error is negligible, owing to the fact that only one of the series 

 of possibilities may with any likelihood occur under a given set of 

 conditions. The observations to be made are taken up in the order 

 in which they occur in the key. 



By means of fertility only the first three species can be identified. 

 Defteiens can not be separated from distichon with certainty on the 

 basis of the grain alone. It may well be ignored, however, because 

 varieties of deficiens are rare. They occur naturally only in Abys- 

 sinia and Asia Minor. In the United States they are found on few 

 of our experimental stations and are almost unknown on farms. The 

 first determination is usually as to whether the sample is 2 rowed 

 or 6 rowed. This can be ascertained readily by the presence or 

 absence of the lateral kernels in the sample. If it is 2 rowed, of 

 course there will be no lateral kernels. As shown in Plate IV, figure 

 1. these lateral kernels can be identified by the twisted character. 

 On the spike their bases lie almost in the same plane as that of the 

 central kernel. Toward the tip, however, they gradually turn in- 

 ward until the planes of the furrows approach a right angle. When 

 the kernel is laid upon the dorsal side, this twist of the furrow is 

 quite conspicuous. The species intermedium usually can be dis- 

 regarded, because of the fact that it occurs very rarely. However, 

 it is separated easily from vulgare. The lateral kernels are not only 

 smaller than those of vulgare, but the tips are either rounded or 

 (somewhat rarely) pointed, showing that neither awn nor hood had 

 been present in the spike. 



The adherence of the flowering glume is, of course, more appar- 

 ent in the thrashed grain than in the spike itself, as the hulled and 

 naked barleys are most easily identified by thrashing. The determi- 

 nation can be made, however, without injury to herbarium material, 

 for the fine cross wrinkling never occurs on the lemmas of the naked 

 forms, and the freedom of the glumes is itself apparent at the junc- 

 ture of the lemma and palet. 



