Origin of Pelorlc Toadflax 475 



Three ways were open to continue my exper- 

 iment. The first was indicated by the abundant 

 harvest from the parent-plants of the mutation. 

 It seemed possible to compare the numerical 

 proportion of the mutated seeds with those 

 of normal plants. In order to ascertain 

 this proportion I sowed the greatest part of 

 my 10 cu. cm. of seed and planted some 2000 

 young plants in little pots with well-manured 

 soil. I got some 1750 flowering plants and ob- 

 served among them 16 wholly peloric individ- 

 uals. The numerical proportion of the muta- 

 tion was therefore in this instance to be 

 calculated equal to about 1^ of the whole crop. 



This figure is of some importance. For it 

 shows that the chance of finding mutations 

 requires the cultivation of large groups of indi- 

 viduals. One plant in each hundred may mu- 

 tate, and cultures of less than a hundred speci- 

 mens must therefore be entirely dependent on 

 chance for the appearance of new forms, even 

 if such should accidentally have been produced 

 and lay dormant in the seed. In other cases 

 mutations may be more numerous, or on the 

 contrary, more rare. But the chance of muta- 

 tive changes in larger numbers is manifestly 

 much reduced by this experiment, and they may 

 be expected to form a very small proportion of 

 the culture. 



