Genetical Studies on Oenothera. V. 



Some Reciprocal Crosses of Oenothera. 



By Bradley Moore Davis, Pliiladelphia, U.S.A. 



University of Pennsylvania. 

 (Eingegangen am 12. Januar 1914.) 



Professor de Tries in liis recent work "Gruppenweise Artbildung", 

 1913, has published data of the highest interest to the experimental 

 workers with Oenothera and to breeders in general. I refer at this time 

 especially to the remarkable differences exhibited by certain hyl)rids of 

 reciprocal crosses, and to the extraordinary results reported when the 

 reciprocals are crossed with one another to give double reciprocal, and 

 with the parent stock to give sesquireciprocal and iterative hj'brids. 



The striking peculiarity of the reciprocal crosses is their marked 

 differences from one another and their great resemblance in certain 

 characters to the pollen parent making them in these featm-es strongly 

 patroclinous. Breeders have, of course, for many years recognized the 

 phenomenon of prepotency on the part of individuals and to a certain 

 extent of species and races when crossed, but de Vries has brought 

 forward cases in which species to a very marked degree exhibit prepo- 

 tencies over others when they are the pollen parents of the hybrids. 

 Breeders had before known that reciprocal crosses are not always ident- 

 ical as to their characters, but general experience had led them to 

 expect similarity whereas in this material of Oenothera de Vries has 

 found very striking differences. Furthermore, de Vries reports that 

 when certain reciprocal hybrids of Oenothera are crossed with one another 

 to give double reciprocals a uniform progeny appears which carries un- 

 affected almost all of the characters of one of the original parents. 



The behavior of reciprocals and double reciprocals outlined above 

 is best illustrated by material that seems likely to stand as classical 

 in the field of genetics. Oenothera biennis pollinated by 0. murieafa 

 gives a uniform Fi generation so strongly patrocliuous with respect to 



Induktive Abatammungs- und Vererbungslehre. XII. \2 



