106 Inheritance in Barley 



The following have been shown to be pairs of allelomorphic characters; 

 (A) and (B), see (a). 

 (A) and (F), see (yS). 



(A) and (G), see (7). 

 (F) and (G), see {6). 



The following may also prove to be pairs of allelomorphic characters; 



(B) and (F), see (e). 

 (B) and (G), see (0- 



The various forms of the lateral floret in barley thus appear to afford 

 another instance of the phenomenon which is now known as " multiple 

 allelomorphism." The work of Morgan on eye-colour in Drosophila, the 

 coat-colour of mice, colour in the maize cob, silk, etc., and the experi- 

 ments of Nabours (8) on Paratettix afford further evidence of this 

 phenomenon — a phenomenon which, other things apart, is of great 

 interest because of its failure to harmonise with the " presence and 

 absence " hypothesis (in its simple form and without appeal to complex 

 linkages). 



Few instances of genetically related degrees of development appear 

 to be so evenly graded as that which has been described here, and a 

 good opportunity presents itself for an attempt to correlate " Mendelian 

 characters " with morphological structures. Such an attempt would 

 have to be based upon a histological study of the various forms of lateral 

 floret at successive developmental stages. The difficulties imposed upon 

 the sorting of F^ types by fluctuations due to environment are very 

 great, and it is unlikely that they will be completely surmounted with- 

 out a histological study of this kind. 



Appendix. Some observations upon the views presented hy Blaringhem 

 (10) concerning the results of certain crosses between Q-row and 2-row 

 barleys. 



Blaringhem has insisted upon the occurrence and upon the im- 

 portance of "L'Heredite en mosaique" (or " Naudinienne "). He has 

 cited the following 6-row x 2-row barley cross as an example. 



H. tetrastichum pallidum was crossed with H. distichum nutans. 

 The Fi consisted of " plantes vigoureuses offrant toutes des 6pis a deux 

 rangs." No more detailed specification of Ft^ characters was recorded. 

 In F^ there were 410 plants. The 6-row type numbered 134, and they 

 were " presque aussi nombreuses que les plantes a deux rangs " ; but 

 what was accepted as the most striking thing about these 6-row plants 



