STUDIES 0\ THE GENETICS OF FLOWER-COLOURS, ETC. 99 



Irnidly clistiuguish tliem exactly by tlioir extei'nal nppearance. 



Tlias we have in /''. 4 Iioiikj- and 7 heterozj'gous plants of orange colom-> 

 ■ttliicli accords, in spite of tli.'ii' small nnmber, fairly well \\itli the calculated 

 numbei-s 3-7 and 7'3 respectively. 



From all above described we see that the difference between orange and 

 wliite-I varieties is due to one factor, and that tliis factor which we call C 

 piixlueos orange colom*. 



Tliough I liave also raised the I'\ generation of tlie above crtjss it will 

 not Ije perhaps worth whUe to describe liei-e its details, and it may suffice 

 simply t<? say that it has fully confh-med the results of the former generations. 



Dining some generations of the above cross certain peculiar phenomena 

 were often met with, whicli might somewhat confuse the Meudehan results 

 oljtained ; thus, for instance, few matjerda and red progeny are produced 

 fi-om seeds taken on orange or even white pljints, and also few orange ones 

 from those taken on white, plants, etc. (naturally seeds being taken on selfed 

 flowers). Tliese phenomena will, according to ray view, chief!}-, though not 

 all, l)elong to the so-called " reverse mutations," and since tliey were observed 

 in many other cases they will be pointed out each time in the course of my 

 description, and discussed together later in a separate chapter (s.p. 121 S). 



Cross n. Yellow xichlie- 1. (PI U, fig. 4 and 8). 

 CCGGrrbbxccgyrrhh F,= CcGyi't'hh: 



In order to study the genotypic constitution of the yellow variety I have 

 done, fe-stly, its cross by the white-I (1915), and sjcontUy, the two reciprocal 

 ci-osses between it and tliu orange (1917j. The -F, -hybrid produced by the 

 Litter crosses has lx)rne flowers where yellow and orange patches of various 

 size are in-egularly scattered on each petal ; in I\ we were however impossible to 

 exactly determine yellow and orange individuals, which we might have expected 

 to have Ijeen produced by segregation, and the experiment was abandoned, 

 at lea.st for a time. -\s to the fii-st of the ci'osses aljove cited, I was much more 

 foi-tunate, though on account of the poor germination of seeds the behaviom: of 

 the i^j-generation could not be so fiolly investigated as might be wished for. 



The i^i-hybrid made by CTOssing it by white-I has borne yellow flowers whose 

 coloiu' is nearly the same, or even more intense than in tin; yellow parent (s. 



