4 MUTANTS AND HYBRIDS OF THE OENOTHERAS. 



exhibited only fluctuating variations of ordinary amplitude, although 

 the last-named feature was not examined by statistical methods. An 

 investigation of this feature is described in the present paper. 



During the earlier cultures, plans were formulated for a somewhat 

 inclusive investigation of the genetic relationships of the various 

 members of the genus, and of the variations, or mutations, which 

 might be found to occur in O. lamarckiana in America, and in the 

 other species of the group. To this end correspondence was estab- 

 lished with collectors in various parts of America and Europe, and 

 material was obtained from such distant points as New Zealand, 

 Mexico, Holland, and Japan. A supply of paraffined paper bags was 

 furnished by Professor De Vries, and later those manufactured for the 

 Station for Experimental Evolution at Cold Spring Harbor were used 

 for inclosing the inflorescences, by which absolutely pure crops of 

 seeds of the species, as well as of the various hybrids, were obtained. 

 All sowings of seeds were made in soil sterilized in an autoclav for 

 three or four hours. A number of the parcels of earth treated in this 

 manner were moistened and kept under proper conditions, but in no 

 instance were any germinations of other Oenotheras seen. In order to 

 economize time it was found most convenient to grow the evening- 

 primroses as annuals, which may be done by germinating the seeds in 

 a propagating house and then transplanting them to the experimental 

 grounds early in May. The earlier cultures were begun about Jan- 

 uary i , but it was found that ample time for the entire development of 

 the plant was obtained if the sowings were made late in February or 

 early in March. 



The portions of the general investigation in which such progress 

 has been made as to warrant the publication of the present paper are 

 as follows : 



(i) Determination of the ancestral habitat and dissemination of 

 Onagra {Oenothera) lamarckiana. 



(2) Description of such species of Onagra {Oenothera) as have 

 been kept under cultivation for one or two seasons in order to facili- 

 tate observation of possible mutants. 



(3) Analysis of the relationship between 0. lamarckiana and 

 other species of the genus by means of hybridizations. 



(4) Estimation of the dominance of parental characters in hybrids 

 of 0. lamarckiana X 0. biennis and O . lamarckiana X 0. cruciata. 



(5) Determination of the recurrence and stability of mutants of 

 the Oenotheras ; description of 0. gigas as cultivated in the New 

 York Botanical Garden. 



(6) Estimation of the fluctuating variability of some of the char- 

 acters of 0. lamarckiana, 0. nanella, and O. rubrinervis. 



