Experimental Pedigree-Cultures 567 



also during the last season (1903). Only gigas 

 appeared but once, but then there is every rea- 

 son to assume that in larger sowings or by a pro- 

 longation of the experiments it might have made 

 a second appearance. 



Is the number of such germs to be supposed 

 to be limited or unlimited ? My experiment has 

 produced about a dozen new forms. Without 

 doubt I could easily have succeeded in getting 

 more, if I had had any definite reason to search 

 for them. But such figures are far from favor- 

 ing the assumption of indefinite mutability. 

 The group of possible new forms is no doubt 

 sharply circumscribed. Partly so by the mor- 

 phologic peculiarities of lamarckiana, which 

 seem to exclude red flowers, composite leaves, 

 etc. No doubt there are more direct rea- 

 sons for these limits, some changes having taken 

 place initially and others later, while the present 

 mutations are only repetitions of previous ones, 

 and do not contribute new lines of development 

 to those already existing. This leads us to the 

 supposition of some common original cause, 

 which produced a number of changes, but which 

 itself is no longer at work, but has left the af- 

 fected qualities, and only these, in the state of 

 mutability. 



In nature, repeated mutations must be of far 

 greater significance than isolated ones. How 



