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 Ké6lreuter and 
Knight were wrong in their assertion that hybrids 
between distinct species were always sterile. Herbert 
considered that only generic or family types were 
