304 Mr Biffen, 



Experiments on the Hybridisation of Barleys. By R. H. 

 Biffen, M.A., Emmanuel College. 



[Read 12 February 1906.] 



The cultivated barleys form a group of elementary species 

 known collectively as Hordeum sativum. The most important of 

 these are H. hexastichum, H. vulgar e, H. zeocriton, H. distichum, 

 and H. decipiens. In the first pair each of the spikelets in the 

 triple groups characteristic of the genus Hordeum is fertile, 

 they differ from one another in the fact that the former has dense 

 ears and the latter lax ones. Both may correctly be described 

 as six -row barleys. H. vulgare is the name given to the group 

 known on the Continent as H. tetrastichum. The use of this latter 

 term is open to the serious objection that it leads to the erroneous 

 impression that the barley is four-rowed owing to the suppression 

 of the median floret of the triplet. H. zeocriton and H. distichum 

 form a similar pair of dense and lax groups differing from the 

 former in the lateral florets, which are staminate only and conse- 

 quently set no grain. These are popularly known as two-row 

 barleys. In the group H. decipiens the reduction of the lateral 

 florets is carried still further, and they are altogether sexless and 

 practically wanting. 



The six- and two-row groups are connected together by the 

 little known H. intermedium, in which the lateral florets, though 

 fertile, are reduced in size and awnless. 



The varieties within the elementary species are distinguished 

 by a number of characters. The most important of these are as 

 follows : 



1. The paleae may or may not adhere to the grain proper. 



The first condition is described as naked, the second I 

 have called " trapped." 



2. The colour of the paleae may be " white," that is, various 



shades of yellow ; or it may be black, brown, or purple. 



3. The grain may be white, bluish-grey, or purple when 



stripped of its paleae. 



4. The awns may be normal or trifurcate. This latter term 



is used to denote the presence of a secondary floret 

 borne on the awn either at its base or some two or three 

 cms. up. 



5. The glumes at the base of each spikelet may be narrow or 



ovate-lanceolate in shape. 



