HOWARD AND HOWARD. 9 



These numbers suggested the existence of two factors in the 

 felted parent and on examination under the binocular dissecting 

 microscope it was observed that the hairs on the chaff of the felted 

 parent were of two kinds — long silky and short hairs. The inter- 

 mediate first generation showed on examination under the microscope 

 that both kinds of hairs were present, but both were diminished in 

 length and in density. From the fact that the ratio 15 : 1 was 

 obtained in the F 2 in all the crosses with smooth chaffed wheats and 

 from the appearance of the Fj generation it appeared probable that 

 these two sorts of hairs were each due to a single factor and were 

 inherited independently. In this case, on Bateson's presence and 

 absence hypothesis, denoting the long factor by L L and the short 

 factor by S S the scheme up to the F 2 generation would be repre- 

 sented by the following : — 



SS L L X s s 1 1 ... ... ... Parents. 



I 

 S s L 1 ... ... ... First (feneration. 



I 

 S SLL + 4SsL~l + 2 Sa LL + 2 SS LI , 



+a a L L+2 s s L 1 + S S 1 1 + 2 S s 1 1+s s 1 1 \ Second generation. 



On this assumption the appearance of these various classes in 

 the F 2 generation and the nature of the progeny in the F 3 would be 

 those shown in the following table : — 



¥.. F 



Constant like the F 2 . 



Series like the F 2 with felted to smooth in 



the ratio 15:1. 

 All variously felted (SS LL + 2 Ss LL + 



ss LL). 

 All variously felted (SS LL + 2 SS LI + 



SS 11). 

 Constant like the F„. 



(1). S S L L both kinds of hairs complete. 

 (2). S a L 1 both sets partly developed as 



in F,. 

 (3). S s L L long factor complete, short 



factor partial. 

 (4). S S L 1 short factor complete, long 



partial. 

 (5). s s L L long factor only complete, 



short absent. 

 (6). s s L 1 long factor partial, short absent. Felted : smooth : : 3 : 1 (ss LL + 2 ss LI + 



ss 11). 

 (7). S S 1 1 short factor only complete, long Constant like the F 2 . 



absent. 

 (8). S s 1 1 short factor only partial, long Felted : smooth . : 3 : 1 (SS 11 + 2 Ss 11 + 



absent. ss 11). 



(9). sail smooth. Constant like F 2 . 



Although the existence of the various groups in the F 2 could be 

 demonstrated by means of the binocular microscope it proved im- 

 possible to analyse this generation completely without an undoubted 



