igi4] DE VRIES— OENOTHERA LAMARCKIANA 347 



rank or even marked varieties, the mutationists would have much 

 stronger evidence in support of the mutation theory than that 

 based on the behavior of O. Lamarckiana."* After conceding this 

 strong position to his adversaries, Davis subjects the results of 

 Stomps to a rather sharp criticism, which, unfortunately, is based 

 upon a confusion of two wholly distinct types, namely, 0. biennis 

 L. var. cruciata^ and 0. cruciata Nutt. He says : "It should be made 

 clear that the form (0. biennis cruciata) is recognized in the more 

 recent taxonomic treatments as a true species sharply distinguished 

 from types of biennis by its floral characters," and "a cross between 

 these types must certainly be regarded as a cross between two 

 very distinct evolutionary Hnes and its product as a hybrid in which 

 marked modifications of germinal constitution are to be expected."* 

 But, as a matter of fact, the Dutch 0. biennis cruciata differs from 

 0. biennis only in the characters of the petals; in all other respects 

 it is wholly the same, and therefore evidently only a subordinate 

 variety of this species. It has not been dealt with in recent 

 taxonomic treatments, since it occurs almost exclusively in the 

 sand dunes of Holland, where it is produced from time to time by 

 mutation from the mother form (first observed in 1900), without 

 having been able until recently to multiply in the field so as to 

 produce a persistent local variety.^ 



On the other hand, O. cruciata Nutt. is quite a different species, 

 with narrow, brownish green leaves, and a different type of branch- 

 ing, of spikes, and of fruits. It grows wild in New York and 

 Vermont, and is well known to all students of the American flora. 

 By some authors it has been considered a variety of O. biennis, 

 and this probably- is the chief cause of Davis' confusion. The 

 character and the behavior of its hybrids with O. biennis have 

 been amply dealt with in my Gruppenweise Aribildung. 



In the experiment of Stomps, the dwarf and semigigas muta- 

 tions were produced by hybrid strains of 0. biennis and 0. biennis 



4 Davis, B. M., Mutations in Oenothera biennis L. ? Amer. Nat. 47:116-121 

 (especially p. 116). 1913; see also 0^. a«. 47:540-596 (especially p. 567). 1913. 

 s Die Mutations-Theorie 2 : 599. 1903. 

 'Amer. Nat. 47:117. 1913. 

 'Die Mutations-Theorie 2:599. i9°3- 



