THE INHERITANCE OF GLUME LENGTH IN 

 TRITICUM POLONICUM. 



A CASE OF ZYGOTIC INHIBITION. 



By W. O. backhouse, 



Economic Botanist to the Argentine Government. 



(With Chart.) 



The sub-species of THticum known as T. polonicum is characterised 

 by long glumes which, in extreme cases, can attain a length of 40 mm. 

 whereas that of an ordinary wheat is in the neighbourhood of 10 mm. 

 only. There is a large number of varieties of T. polonicum known, 

 varying considerably in minor characters such as colour of leaf, colour 

 and shape of grain, degree of felting, etc., also in glume length itself, 

 some having an average length of about 19 mm., others as high as 

 28 mm. The sub-species T. polonicum hybridises easily with both 

 T. durum and turgidum and shows \ by the total lack of sterile indi- 

 viduals in F2 when crossed with varieties of the former, that it might 

 be considered, genetically speaking, merely an aberrant form of the 

 sub-species T. durum. The result of hybridising the long and the 

 short glume lengths is a first generation intermediate in this respect, 

 splitting in the second into long, intermediate and short in the ordinary 

 1:2:1 ratio, but not, in a manner possible to classify by eye and 

 necessitating the plotting of a curve to show the segregation. 



When at Verrieres, in 1911, through the kindness of M. Ph. de 

 Vilmorin, the writer was able to examine a collection of varieties of 

 T. polonicum grown there and was struck by the fact that there were 

 none with perfectly smooth glumes and, furthermore, that the shorter 

 the glume of the variety, the more felted did it seem to be. The longest 

 glumed varieties, being only faintly pubescent, would roughly speaking 



1 R. H. Biffen, Journal of Genetics, Vol. v. p. 225, 



