MUTATIONS, VARIATIONS. AND RliLATIONSHlPS 



OP THE OHNOTHHRAS. 



By D. T. MacDougau, A. M. Vail, and G. H. Shull. 



SCOPE OF INVESTIGATION. 



The Oenotheras have furnished so much evidence of importance in connec- 

 tion with saltatory action in heredity that it has been deemed important to 

 continue the cultural investigation of the group begun in 1902. 



Sseds representing the spscies in cultivation in the principal botanical 

 gardens of the world have been procured, and these, in addition to a large num- 

 ber of forms native to eastern North America, have been grown in guarded 

 cultures. 



Attention has bsen paid to the occurrence of mutants in Oenothera lamarck- 

 ian2 with a view to testing: the coefficient of mutabilitv and the influence of 

 environmental conditions on mutation. Extensive sowings have been made 

 for the purpose of finding derivatives hitherto undetected, with a coefficient of 

 mutability so small as to have escaped observation. Descriptions of known 

 mutants have been made independently for the purpose of comparison with 

 supposedly identical forms in Amsterdam and of facilitating observations 

 of all kinds upon the subject. 



Many important relations between mutants and their parents may be most 

 advantageously considered by statistical methods, and the studies begun by 

 one of the authors in 1904 have been continued and extended to include addi- 

 tional mutants. The height and branching of the stems and the width and 

 length of the leaves have been again taken into account, but owing to the 

 great susceptibility of these organs to variation in direct response to environ- 

 ment, measurements have also been made upon the buds. The lesser varia- 

 tion of the latter in correlation with vegetative characters makes them much 

 more satisfactory for the study of hereditary relations, and it is clear that 

 their statistical study in connection with pedigree-cultures will demonstrate 

 in several generations the permanence or evanescence of the mutant types 

 and give decisive answers to such questions as the relation between fluctua- 

 tion and mutation and the "fixing" of variations through self-fertihzations 

 or their disappearance through crossings. 



