THE MUTATION THEORY 



357 



Only one form, O. scintillans, that appeared eight times, is not 

 constant as are the other species. When self-fertiUzed its seeds 

 produce always three other forms, 0. scintillans, O. oblonga, and 

 O. laniarckiana. It differs in this respect from all the other elementary 

 species, which mutate not more than once in ten thousand indi\'iduals. 



Genera- 0. rubri- O.Lamarck- 0. scintil- 



tions 0. gigas 0. albida O. oblonga nervis iana 0. nanella 0. lata lans 



Gen. 8 

 1899 



Gen. 7 

 1898 



Gen. 6 

 1897 



Gen. 5 

 1896 



Gen. 4 

 1895 



Gen. 3 

 1890-91 



Gen. 2 

 1888-89 



Gen. I 



1886-87 



Mutants and Number observed in 

 different years 



0. Lamarck- Mutants and Number 

 iana observed in different years 



The mu- 

 tating 

 stem form 



Fig. 59. — Diagram showing in condensed form the genealogy of the Oenothera 

 Laniarckiana family and its various mutants during successive years. The numbers 

 under each type represent the number of new types observed each year. (From 



Tower.) 



From the seeds of one of the new forms, G. laevifolia, collected 

 in the field, plants were reared, some of which were 0. lamarckiana and 

 others O. laevifolia. They were allowed to grow together, and their 

 descendants gave rise to the same forms found in the laniarckiana 



