Oenothera Leptocarpa. 353 



to stand more upright, and not to open so wide as those 

 of the parent species (compare Plate III with Plate I). 

 In other respects they have the same structure, and the 

 stigmas stand up well above the anthers. The color of 

 the flower is a paler shade of yellow. The fruits do not 

 attain the length or the stoutness of those of 0. La- 

 marckiana, and as a rule set little seed. 



The gray color, which, like that of 0. rttbrinervis is 

 not due to increased hirsuteness, but to the swelling 

 of the outer wall of the ordinary epidermis cells, ex- 

 hibits a high degree of individual variability, sometimes 

 indeed to such an extent that doubt may arise as to the 

 proper diagnosis, a doubt which however can always 

 be dispelled by the examination of later stages. 



§ i6. OENOTHERA LEPTOCARPA. 



The foregoing examples have shown us that muta- 

 tions arise from Oenothera Lamarckiana in proportions 

 which vary from about 1 % to less than 0.1 %. We have 

 further seen that the same mutations recur regularly in 

 the same mutation period. 



It follows from this that a careful study of such a 

 period wnll soon reveal the commoner mutants which 

 the species in question is producing. Then we have to 

 look for the rarer ones ; and for this purpose much more 

 extensive sowings must be made. 



If these rare mutations can be recognized as seedlings 

 or at any rate as young rosettes, all that we have to do is 

 to sow seed on a large scale, transplant any seedlings 

 which exhibit any abnormality and throw away those 

 which have not mutated. If this method is adopted 



