No. 547] GENETIC AL STUDIES ON (ENOTEEBA 385 



biennis and grandiflora so far tested in the F 2 genera- 

 tion (briefly described later in the paper) showed clearly 

 that there is a segregation of flower size. Some types of 

 flowers appeared in the F 2 that were even larger than the 

 grandiflora parent species and as large as the largest 

 Lamarckiana; others were smaller than the flowers of the 

 F 1 hybrid parent, although none were so small as the 

 biennis parent species. Between the large and the small- 

 flowered F 2 hybrids was an apparently perfect range of 

 intermediates. 



Gates ('life) has criticized the comparison of the 

 flowers of my hybrid plants 10.30La and 10.30L& to those 

 of Lamarckiana (Davis, '11) on the ground that their 

 measurements were too small (petals 2.2 cm. long), being 

 unwilling to recognize the existence of small-flowered 

 types of Lamarckiana. He apparently, however, fails to 

 appreciate that the problem is only in part what may 

 appear in the F x generation. It is the behavior of the 

 hybrids in the second and later generations that will 

 demonstrate the possibilities of the double organization 

 of the F 1 hybrid, and the results of my cultures of the F 2 

 generation indicate that forms with flowers fully as large 

 as those of the largest-flowered Lamarckiana may be 

 readily obtained in abundance. It may prove more diffi- 

 cult to establish in the hybrids certain points of stem 

 coloration and leaf form, but my later studies indicate 

 that these results will depend chiefly upon proper 

 discrimination in the choice of parents for the cross, 

 especially among the large variety of biotypes included 

 in biennis. 



3. Further Races of (Enothera biennis L. 

 I have discarded for experimental purposes the races 

 biennis A and biennis B which were used in the first 

 • Tosses with 0. grandiflora (Davis, '11). These have 

 been supplanted by biotypes much more favorable for 

 the purposes of the investigation. Among the American 

 wild forms of biennis the best so far obtained is biennis D 



