ON TRIPLE HYBRIDS. 



Twin hybrids arc produced when the pollen of Oenothera Lamarck- 

 iana or of one of its derivatives is crossed with the European sub- 

 species of 0. biennis or of 0. muricata. These twins appear in about 

 equal numbers and are constant in succeeding generations. One 

 of them, 0. laeta, is broad and smooth leaved ; the other, 0. velutina, 

 is more hairy and has furrow-shaped leaves^). 



Triple hybrids may be produced by combining this phenomenon 

 with the hereditary qualities of 0. lata and 0. scintillans. Both of 

 them originated in my garden from 0. Lamarckiana. 0. lata is 

 female, its anthers are barren. 0. scintillans is an inconstant species 

 which repeats its type only in one-third or two thirds of its offspring. 

 Both of them, when pollinated by 0. Lamarckiana, give a mixed 

 progeny, only part of which is like the mother^). 



In order to get triplets, therefore, we have to cross 0. lata or 0. 

 scintillans with some species which will split them into laeta and 

 velutina (as it would do 0. Lamarckiana itself or some others of its 

 mutant species), and which, moreover, does not prevent them from 

 repeating their own type in their progeny. The triplets will then be 

 0. laeta, 0. velutina, and 0. lata. The first two will drop the special 

 character of the mutant-parent {Opera VI, p. 474), but all three 

 will be intermediate hybrids between 0. Lamarckiana or 0. lata and 

 the species used as the other parent, 



I found that 0. strigosa Rydberg, 0. Hookeri T. and G., and the 

 common American subspecies of 0. biennis L. comply with these 

 requirements. The experiments to be described in this article are 

 limited to the effects of their pollen on 0. lata and 0. scintillans. 



0. strigosa Rydb. has very small flowers, of the size of those of 

 0. muricata, but in less dense spikes. They open their anthers two 

 or more days before unfolding the corolla, and the pollen comes 

 in contact with the whole outer surface of the stigma and causes 

 fertilization. The leaves are bluish green and furrow-shaped, and 

 the tip is bent sideways. The tops of young shoots, when seen from 

 above, therefore, present the aspect of a wheel with spokes all curved 



i) Opera VJ. p. 472. 



2) Die Mutationstheorie. Vols. 1 and Ji. 



