Principles of Heredity 159 



principle at once gives a complete account of the whole, 

 this is scarcely necessary, though the matter is full of 

 historical interest. 



Crossing a white pea with a very large grey purple- 

 flowered form Knight (21) found that the peas so produced 

 "were not in any sensible degree different from those 

 afforded by other plants of the same [white] variety ; 

 owing, I imagine, to the external covering of the seed (as 

 I have found in other plants) being furnished entirely by 

 the female*." All grew very tallf, and had colours of 

 male parent J. The seeds they produced were dark grey. 



" I had frequent occasion to observe, in this plant [the 

 hybrid], a stronger tendency to produce purple blossoms, 

 and coloured seeds, than white ones ; for when I introduced 

 the farina of a purple blossom into a white one, the whole 

 of the seeds in the succeeding year became coloured [viz. 

 DR x D giving DD and DR\ ; but, when I endeavoured 

 to discharge this colour, by reversing the process, a part 

 only of them afforded plants with white blossoms ; this 

 part sometimes occupying one end of the pod, and being at 

 times irregularly intermixed with those which, when sown, 

 retained their colour " [viz. DR x R giving DR and RR] 

 (draws conclusions, now obviously erroneous ||). 



In this account we have nothing not readily intelligible 

 in the light of Mendel's hypothesis. 



The next evidence is supplied by an exceptionally 

 complete record of a most valuable experiment made by 



* Thus avoiding the error of Seton, see p. 144. There is no xenia 

 perhaps because the seed-coat of mother was a transparent coat. 



t As heterozygotes often do. 



Dominance of the purple form. 



Dominance of the grey coat as a maternal character. 



|| Sherwood's view (J. R. Hort. Soc. xxu. p. 252) that this was the 

 origin of the "Wrinkled" pea, seems very dubious. 



