404 THE WHEAT PLANT 



The progeny of these in F 3 is indicated below : 



F 2 generation. F 3 generation. 



( 5 very dense compactums . . 5 constant compactums. 



j'i8 constant compactums. 

 56 compactums .... - 38 segregating into compactums and non- 



compactums. 

 5 compactum-\ike ... 5 segregating into compactums and non- 



compactums. 



28 not compactums . . . Only non-compactum progeny, but of 



variable ear length and density. 



The F 3 results show that the F 2 generation consisted of 23 homozygous 

 compactums, 43 heterozygotes, and 28 homozygous non-compactums , 

 suggestive of the simple monohybrid 1:2:1 ratio. 



Similar gradation of density of ear between the compact and laxer- 

 eared segregates occurred in the F 2 generation of the cross " Binkel " x 

 " Bore " wheat, but the nature of the plants of the F 2 generation was 

 cleared up in the F 3 progeny : 



F 2 generation. F 3 generation. 



f 25 constant compactums. 

 46 compactums . . . . : 21 splitting into compactums and non- 



compactums. 

 31 less dense compactums . . Splitting into compactums and non- 



compactums. 



1 1 Binkel " Squareheads " . . Do. 



i " Squarehead "... Do. 



37 plants with lax ears . . . Descendants all non-compactums, but 



exhibiting considerable variation 

 in ear-density. 



The results of the F 3 generation show that the F 2 consisted of 25 

 homozygous compactums, 64 heterozygotes, and 37 homozygous non- 

 compactums, approximating as in the previous cross to the 1:2:1 ratio. 



The results obtained by Nilsson-Ehle led him to believe that in the 

 long lax-eared " Land wheats " two independent factors L x and L 2 are 

 present, each of which, by itself, increases the length of the internodes of 

 the ear ; when both factors are present their effects are cumulative. 



The dense ear of T. compactum he considers due to a factor C which 

 shortens the rachis-internodes and is epistatic to L x and L 2 . 



On this hypothesis plants of the genetic constitution CL^L^, CL^, 

 C^Lo, as well as those containing the C factor alone (Cljlg), would have 

 short compactum ears, though not all of equal ear-density, since the L 

 factors are not completely masked by the presence of C. 



From analysis of his results he concluded that the Swedish Binkel is a 



