No. 561] GENETIC AL STUDIES ON ANOTHER A 569 



found in grandiflora, and undoubtedly present in some of 

 the large-flowered Oenotheras of the west and southwest. 

 If the plant of Dr. Gray was representative of the cul- 

 tures of Carter and Company the evidence indicates that 

 their forms became greatly modified during the quarter 

 century before the time when De Vries began his studies, 

 at about 1886, and isolated the type which we know to-day 

 as Oenothera Lamarckiana De Vries. 



On the experimental side of the problem of the origin 

 of De Vries 's Lamarckiana we have evidence of its hybrid 

 nature from various sources. The recent analytical 

 studies of Heribert-Nilsson ('12), previously mentioned, 

 show that certain characters of Lamarckiana behave in a 

 manner suggesting their association in a complex hybrid 

 that is still throwing off segregates. His conclusions that 

 Lamarckiana is a polymorphic species is supported by 

 my own experience in isolating certain biotypes from ma- 

 terial of De Vries. The "twin hybrids" produced when 

 Lamarckiana or certain of its derivatives furnish the 

 pollen of a cross with biennis or muricata indicate, as 

 suggested by several critics, that different types of 

 gametes are formed by Lamarckiana. 



My own studies on hybrids between forms of biennis 

 and grandiflora have reached an interesting point. I 

 have not been able to synthesize by direct crosses, from 

 wild stock so far obtained, any hybrid with all of the 

 characters of Lamarckiana in the same plant, although I 

 believe that all of the important taxonomic characters of 

 Lamarckiana have been represented in some of my 

 hybrids. It is, however, probable that more favorable 

 parental types will in time come to hand. For example, 

 a form, with the habit and foliage of the Dutch biennis 

 and with the stem coloration of Lamarckiana, which the 

 Dutch biennis apparently has not, would furnish very 

 favorable" material. In the meantime I have the possi- 

 bility of crossing my hybrids back with certain wild 

 species and of crossing the hybrids with one another. In 

 this way it may be possible to bring into one plant all of 



