Oenothera A lb id a. 351 



tip. During the growth the leaves of the rosettes in- 

 crease in breadth as a rule (Fig. 76) whilst those of the 

 stem become narrow again (Fig. 54a on page 295). 



It is always easy to recognize albida mutants by the 

 characters I have described. I have cultivated many of 

 them beyond this stage, especially in 1895 and the fol- 

 lowing years, in the hope of getting them to flower and 

 set seed. And in this way I had ample opportunity of 

 testing the accuracy of my diagnosis. 



The ease with which this species can be recognized 

 as quite a young plant makes it a convenient one for the 

 study of the relative frequency of its origin from O. 

 Lamarckiana and other species. The result of this in- 

 vestigation was that this frequency, this coefficient of 

 mutation, turned out to be very different in different 

 cases and to be subject to even greater fluctuations than 

 those exhibited by the three species described above 

 (0.01 % for O. gigas, 0.1 fo for rnbrinervis and 1 % 

 for oblonga). 



The two tables that follow bring this out. I include 

 in them figures that have already been given in §§ 2-5. 



INDIVIDUALS OF OENOTHERA ALBIDA WHICH HAVE 



ARISEN BY MUTATION. 



I 



SOURCE DATE TOTAL 



SEEDLINGS 

 ALBIDA % ALBIDA 



O. Lamarckiana-isimWY . 1895-1899 28,500 56 0.2 

 O. Lamarckiatia, plants 



from crosses .... 1898 4,599 2 0.05 

 A lateral branch of the 



Lamarckia7ia-isim\\Y . 1895 10,000 255 2.5 



O. lata 1900 2,000 42 2.1 



O. lata 1896-1899 751 31 4.0 



O. Lamarckiana, biennial 1896 164 15 9.0 



