ON SOME HYBRIDISATION EXPERIMENTS 183 



10 in the other, thus breeding true to this character. However, as 

 the numbers were very small it is not impossible that self green plants 

 in very minute numbers may occur in the progeny of variegated plants 

 in CoUinsia as is the case in Mirabilis (Correns2.), Aqiiilegia (BaurI.), 

 maize (Miles 4.) and Plantago (Ikeno 3.). 



As to the amount of yellow colour in the variegated plants there 

 was a very considerable variation. Of the 10 Fo-plants 3 were yellow 

 without or only with a very small amount of green. These plants 

 died very soon after the germination. Of the rest 2 plants showed 

 only small spots and stripes of yellow, but 5 had the yellow areas 

 much larger. This suggests a Mendelian segregation and can be ex- 

 plained through the hypothesis of a gene, /, which increases the 

 amount of green in variegated plants but onh' to a certain degree so 

 that self coloured plants are not formed, and of its allelomorph, i, 

 which does not have this effect. Then »-plants would be altogether or 

 nearly yellow and die very soon, the li- and the //-plants would be 

 variegated and be able to live. The numbers found, 7 variegated with 

 much green and 3 nearly yellow, agree well with the calculated ones on 

 the 3 : 1 ratio, 7,5 and 2,5+1,369. Perhaps the /i-plants would be di- 

 stinguishable from the //-plants in the smaller amount of green as is 

 suggested by the facts (found : 2 with small yellow parts, calculated : 

 2,5). In order to try to solve this problem I self- pollinated some plants 

 with different amount of yellow, and from two of them some seed was 

 obtained. 



VI — 5 — 1 with small yellow areas gave when selfed 2 variegated 

 with much green colour and 1 nearly yellow, early dying. 



VI — 5 — 5 with larger yellow areas gave when selfed 8 variegated 

 with much green colour and 2 nearly yellow, early dying. 



Thus all the plants were more or less variegated but also here a 

 segregation occurred in viable plants with much of green and almost 

 yellow, non-viable plants. It is, therefore, very probable that these 

 two sorts of variegated plants are genotypically different. The num- 

 bers in F3 (10 with much of green, 3 nearly yellow) are also in very 

 close accordance with the calculated ones on the ratio 3 : 1 

 (9,75 and 3,25 + l,56i). As the two progenies showed the same segregation 

 although the two Fa-plants differed in the amount of yellow, it does 

 not seem possible to distinguish the //-individuals phenotypically from 

 the /{-individuals. 



I have used another variety of C. tinctoria for hybridisation ex- 

 periments. The flowers of the plants usually raised were lilac on the 



Hereditas I. 13 



