KNIGHT 169 



Knight failed to notice. He observed, however, that 

 white crossed by a purple strain invariably gave purple, 

 whilst the cross-bred purples, when crossed again with 

 white, yielded some white and some purple plants. 



In 1822 John Goss recorded the fact that a ' blue ' 

 pea crossed with a * white ' yielded from the crossed 

 flowers pods with white seeds only, the seeds contained 

 in other pods upon the same plant being, of course, 

 blue. The plants produced from the white seeds bore 

 some pods with all blue, some with all white, and many 

 pods with both white seeds and blue ones ; and a 

 coloured plate is given which shows one of the latter 

 pods together with its contents. The blue seeds, when 

 sown separately, yielded plants which produced blue 

 seeds only, but plants arising from the white seeds 

 yielded a mixture of blue and white seeds. 



Knight pointed out quite correctly that the colours 

 of the seeds which are here referred to are occasioned 

 by the colour of the cotyledons or seed-leaves of the 

 pea, which are visible through the semitransparent 

 seed-coat. Green cotyledons give rise in this way to 

 a bluish appearance, whilst, when the cotyledons are 

 yellow, the resulting appearance of the seed is described 

 as whitish. 



The Hon. and Rev. W. Herbert was another observer 

 who made many important experiments in hybridiza- 

 tion towards the beginning of the nineteenth century. 

 These led him to the conclusion that Kolreuter and 

 Knight were wrong in their assertion that hybrids 

 between distinct species were always sterile. Herbert 

 considered that only generic or family types were 



