2 BOTANICAL GAZETTE [january 



occur after hybridization, and especially with those which appear 

 in the first hybrid generation. If we apply this view to the twin 

 hybrids laeta and velutina, the possibility is at once revealed that 

 the components of this group of characters might not always be 

 so indissolubly connected, and that some deviating combination 

 of these qualities might still produce a mutant laeta, different from 

 the type of Lamarckiana. As a matter of fact, a pure and com- 

 plete mutant velutina has appeared in my cultures, but a laeta 

 has never been seen as a mutant. In crossing this velutina with 

 the parent species, however, twin hybrids arose, one of which may 

 be designated as laeta, as will be shown later. 



The question whether the characters of mutants and of hybrids 

 among the Oenotheras are single or built up of a less or greater 

 number of theoretically independent units now seems to be one of 

 principal interest to me. Until now, however, the analysis of 

 the qualities of the twin hybrids laeta and velutina has been diffi- 

 cult and unreliable on account of the presence of the hereditary 

 qualities of their other parent. We can make inferences from these 

 by comparing the twins issued from the crosses of different species 

 with O. Lamarckiana, but we can hardly expect to get a complete 

 analysis in this way. The mutant velutina is free from these 

 specific admixtures, and therefore may afford a better material for 

 experiments in this direction. I intend to study it from this point 

 of view by means of a number of crosses, most of which I made 

 during the summer of 191 5, and shall give here only a description 

 of the mutant itself, and of those hybridizations which give proof 

 of its right to the name of velutina. 



In order to avoid the confusion which might easily arise from 

 the similarity of the names O. Lamar ckiana hyb. velutina and O. 

 Lamar ckiana mut. velutina, I will give a synonym to the latter and 

 call it 0. Lamarckiana mut. blandina, or briefly 0. blandina. In 

 descriptions the use of this latter term will be obviously the easier. 

 O. blandina has throughout its life and in all its organs a paler tinge 

 than O. Lamarckiana. 



O. blandina is, in all respects and at every stage of its evolution, 

 strikingly different from O. Lamarckiana and easily recognizable. 

 Its marks become visible with its very first leaves, when still in the 



