MUTATIONS, VARIATIONS, AND RKLATIONSHIPS OF THE) OENOTHERAS. 6 1 



Purely fertilized seeds of the mutant branch and of the main stem were 

 obtained, and these were sown late in September, 1905. Those of the main 

 stem came true to the type of the main stem, that is, to O. ammophila. All 

 of the progen}^ obtained from the purely guarded seeds of the sport conformed 

 strictly to the biennis type (plate 9). 



THE INDUCTION OF MUTATIONS. 



One of the most important problems confronting the investigation in this 

 subject is that of the localization of the mutations in the life-history of the 

 plant. If we could fix upon the exact stage in which the direct changes 

 occurred, we then would be in a position to examine the protoplasts con- 

 cerned with a view to ascertaining what changes ensue in the chromosomes in 

 connection with saltations in inheritance. Furthermore, opportunity would 

 also be offered for attempts to determine the factors which operate as stim- 

 uli, or loosing agents in setting the mutations free. 



A theoretical consideration of the subject seemed to indicate that the 

 changes constituting the mutations which give rise to atypic seedlings took 

 place in a stage previous to the reduction divisions in the embryo-sac or in 

 the pollen mother-cell. It was planned, therefore, to subject these structures 

 to the action of chemical agents at a time before fertilization had occurred. 

 The attempt was made to secure two forms of stimulation by using some solu- 

 tions of high osmotic value, and other mineral compounds which are stimu- 

 lative in low concentrations. A desideratum in such experimentation was to 

 use plants in which a large number of ovules were to be found in one ovarial 

 cavity. The solutions were injected into the ovaries by means of a physician's 

 hypodermic syringe. Operations of this character were carried out with 

 Begonia rotundifolia and with a species of Cleome, but with negative results, 

 and injections were also made into the central placenta of a number of flowers 

 of Abidilon abiitilon, but in all cases at a very late stage, and so far no results 

 have been obtained with this plant. It is being used in a new series of experi- 

 ments, however, which, with improved technique, may be expected to furnish 

 some interesting material. 



Attention was next turned to several species of Oenothera which were 

 being cultivated in pure pedigreed strains in the experimental garden. 

 Solutions of copper sulphate of i to 400,000 were injected into ovaries of 

 lamarckiana immediately previous to pollination and the pistils were purely 

 pollinated. The capsules formed from ovaries treated in this way were vari- 

 ously distorted as a result of the wounding, but a large crop of perfect seeds 

 was matured, which were sowed in September, 1905. A careful census of the 

 seedlings late in November made it appear that in the small number of mutants 

 present the usual mutants of this species occurred in normal proportions. 



