14 Inheritance in the Japanese Convolvulus. Part II 



and half purple ; in the other, half purple and half red. His opinion on 

 the occurrence of this phenomenon is that it is due to a somatic mutation, 

 that is a change in genetic constitution rather than a segregation • of 

 genetic factors, and this somatic mutation may be a gain of at least one 

 new factor, the loss of a factor, or the permanent modification of a factor. 

 Moreover he brings against the segregation hypothesis the following 

 considerations. "If a dominant character appears as a bud sport, in 

 material known to be homozygous with respect to a recessive character 

 that is alleloraorphic to the dominant character in question, it seems 

 clear that a somatic mutation is the responsible agent.... It would be 

 interesting to know whether recessive bud sports actually occur much 

 more frequently in heterozygous than in homozygous material. If this 

 is found not to be the case, it will have an important bearing upon the 

 problem of whether bud sports are mutations or segi'egations, for the 

 latter would occur only in heterozygous material." 



Above we have described three cases of Japanese Convolvulus where 

 the dominant character has arisen in material known to have the recessive 

 characters. Accordingly it is impossible to consider this phenomenon 

 merely due to the segregation of factors, but it will be necessary to think 

 that there occurred some change in the somatic cells which have had 

 recessive characters. I did not cultivate the offspring of the plant which 

 produced a deep scarlet coloured part in a deep magenta coloured flower, 

 so that I cannot decide whether the original colour was in a homozygous 

 or a heterozygous condition. If in the latter condition we may consider 

 the phenomenon due either to the segregation of factors or to somatic 

 mutation, but if in homozygous condition the latter would seem to be 

 the real cause of the phenomenon. 



3. The relation between leaf-colour and the growth habit of plant-body. 



The parent B, which has green leaves, grows vigorously. It has a 

 big and long stem with long internodes, and side branches appear at 

 the fifth or sixth leaf axil from the base. A on the other hand has a 

 slender stem with side branches appearing at the second or third leaf- 

 axil and flowers opening earlier than B. The F^ plant has characters 

 similar to those of B, at least as regards the above stated points. In 

 the F<i generation also these characters were found to be associated with 

 the leaf-colour, though I did not undertake to measure. It is quite clear 

 that the weak gi-owth of yellow-plant is due to small amount of green 

 pigment in them. 



