MUTANTS AND HYBRIDS OF THE OENOTHERAS. 1 7 



definitely stated, since no living material of the latter has been exam- 

 ined. The only characters of the hybrid clearly derived from the 

 pistil-parent are the relative length of the main axis and the general 

 habit of branching. It is to be said on the other hand that the cruciata 

 characters to which the general aspect of the plant is largely due are 

 without exception more or less modified. The relative length of the 

 stamens and pistils was seen to vary so that some of the flowers were 

 capable of self-pollination, while in others the chance of pollination 

 without the aid of external agencies was extremely small, so that it 

 might be said that in some branches of the plant the lamarckiana 

 character was dominant, while in others the cruciata self-fertilizing 

 capacity was shown. A similar range of partial variability will be 

 described in one of the hybrid races of the O. lamarckiana XO. biennis. 

 O. lamarckiana X O. biennis. The results of the crosses made in 

 the New York Botanical Garden were much more diversified than 

 those made by De Vries, who obtained what he designates as a 

 typical unilateral hybrid as a result of fertilization of 0. lamarckiana 

 by 0. biennis grandiflora. He says (De Vries, 1903, p. 31) : 



The hybrid of Oenothera biennis (O. biennis grandiiiora) and 0. lamarckiana 

 resembles the first so strongly that they can hardly be distinguished from one 

 another. I have made this cross partly in 1894 and partly in the summer of 1899, 

 and in the last-named year partly with O. lamarckiana from my own cultures, 

 and partly from the same species grown from purchased seeds. In all cases I 

 used O. lamarckiana as the mother. The stamens were taken from flowers of 

 plants in the open (from unopened buds), and from plants of my own cultures 

 in the last-named period. The bastards were of a single type, and were inter- 

 changeable with O. biennis (O. biennis grandiiiora) , not only in the rosettes, 

 but also in the flowers and ripe fruit. I had about 50 flowering plants in 1895, 

 and about 70 -)- 60 in the two series in 1899, making altogether about 180 speci- 

 mens in bloom in addition to some with young stems and rosettes only (bien- 

 nials). Some differences were seen, but they were not so marked or so important 

 that a description could be made of them. 



I harvested some seeds in 1895, which were secured by artificial pollination, 

 and the second generation was grown from these in the summer of 1896. These 

 repeated, in the 50 specimens coming into bloom, only the characteristics of the 

 first-named parent (biennis). 



Similarly the pollination of 0. lamarckiana by 0. mitricata resulted 

 in a monotypic unilateral hybrid which approximated the pollen- 

 parent. 



Four distinct types were distinguishable in the hybrid in New 

 York, and the different forms could be recognized in a very early 

 stage of the seedlings. All of the individuals were easily seen to be 

 grouped around the types mentioned, and no intermediate or inter- 

 grading forms were found. The number of individuals brought to 



