THE AMERICAN NATURALIST. [Vol. XXXVII. 



Being desirous of testing the general facts of mutation as 

 illustrated by the behavior of the Oenotheras under environ- 

 mental conditions different from those at Amsterdam, seeds of 

 CE. lamarckiana, CE. rubrinervis, CE. lata, (E. uanella, (E. 

 brevistylis, and (E. gigas were procured from Professor DeVries 

 and these were placed in soil in the propagating houses of the 

 New York Botanical Garden May 15th, 1902. Germination fol- 

 lowed in a few days, and a number of individuals ranging from 

 fifteen to forty of every species were pricked out and suitably 

 repotted from time to time. The cultures were examined three 

 to seven times per week except during February, 1902, and July, 

 1903. The amount of work necessary to make minute and exact 

 observations on all of the above forms being too great a demand 

 upon my time, chief attention was devoted to a comparison of 

 the parent type with rubrinervis and nanclla, two mutant forms. 



continuously upon the habits of the growing plants and formal 



First stage. — July nth, 1902. The plantlets were nearly 

 two months old and still retained the cotyledons. 



Second stage. — October 15th, 1902. A distinct tap root 



Third stage. — June ist-ioth, 1903. Adult rosettes had 

 been formed, and the smaller leaves which appear around the 



Fourth stage.— August ioth-isth, 1903. A number of 

 inflorescences had been produced and flowers were opening daily 

 in great profusion on some of the forms. Some of the inflores- 



by means of artificial transfer of pollen. 1 



The more apparent anatomical differences among the forms 

 examined are shown quite strikingly by the series of photo- 

 graphs and drawings which illustrate this article. 



not undergone noticeable alteration during the long period it 

 has been under exact observation. The seeds from which the 



