78 De Vries : Atavistic Variation in Oenothera 



tation, in the same way as many of our ordinar}- varieties of gar- 

 den plants have been produced, the other is by crossing, which is 

 perhaps a still more common source of new^ garden varieties. 



Both possibilities seem to me to be of some interest, since they 

 bear directly on the great question of the internal causes of incon- 

 stancy in general. For in my variety the petals do not vary ac- 

 cording to Quetelet's law, about a mean, which lies somewhere 

 between the obcordate and the linear form, producing petals of 

 which the majority do not essentially differ from this mean, whilst 

 the extremes are very rare. Quite on the contrary, the obcordate 

 and the linear petals seem to be two alternating types only united 

 by rare intermediate steps. 



In case my variety originated by a mutation, we would there- 

 fore have an imperfect one, producing the new type only in part of 

 the individuals and remaining true or returning to the pure form of 

 Oenothera cruciata in the others. In many points this case would 

 be analogous to that of Oenothera scintillans, which originated in 

 my garden from 0. Lamarckiana, but which, though artificially 

 pollinated with its ow n pollen, returns in each generation in often 

 a relatively large part of the individuals to the original type. 



In case my variety originated by a cross, it should first be re- 

 marked that the supposed hybrid is not intermediate between 0. 

 cruciata and some allied species, but that it has, as far as I can 

 judge, all the characters of the former, the constancy in the form 

 of the petals excepted. I have endeavored to show in my " Mu- 

 tations-theorie " (Part II., p. lOo) that O. muricata is probably the 

 only species which could have given such a hybrid with the 0. 

 cruciata. Now it is clear that having once obtained seeds froir 

 the original and constant 0. cruciata, I possess the materials to 

 bring about this crossing and also those with other allied species, 

 and to try whether it will be possible to get an inconstant hybrid 

 in this way. I propose to do so, but from what I know of my 0. 

 cruciata varia and of the hybrids I have made of it with more than 

 one other species, it is very improbable that the hybrid 0. cruciata 

 X O. muricata will be as a rule inconstant. It is far more probable 

 that it will exhibit the dominant character, which must be the broad 

 petals, and either give a constant progeny with this feature or split 

 up according to Mendel's laws. I take the broad petals to be 



