HERITABLE DIFFERENCES 45 



Lata, since it produces only female flowers and so 

 cannot be self-fertilized, had constantly to be crossed 

 back with the parent lamarckiana, when it produced 

 from 15 to 20 per cent lata and 80 to 85 per cent 

 lamarckiana. 



Finally, scmtillans which appeared at three separate 

 times proved constant only in its inconstancy because 

 it invariably produces a heterogeneous progeny. The 

 1895 plant gave 53 per cent lamarckiana, 35 per cent 

 scintillans, 10 per cent oblonga, and 1 per cent lata. 

 One of the 1896 plants gave 51 per cent lamarckiana, 

 39 per cent scmtillans, 8 per cent oblonga, 1 per cent 

 lata, and 1 per cent nanetta, while another 1896 plant 

 gave only 8 per cent lamarckiana, but 69 per cent 

 scmtillans, 21 per cent oblonga, and 2 per cent of 

 nanella and lata together. 



These different kinds of evening primroses are dis- 

 tinguished from each other by features which are un- 

 mistakable even to the uninitiated. The old-time sys- 

 tematist would undoubtedly have regarded them as dis- 

 tinct species. 



DeVries distinguishes four categories among the 

 CEnothera mutants, the first three of which are 

 quite likely to maintain themselves in nature. They 

 are: 



1. Progressive species, (gig as, rubrinervis) , due to 



the addition of certain characteristics ; 



2. Retrogressive varieties, (nanella, Iceviflora, bre- 



vistylis), characterized by the loss of some- 

 thing that was present in the parent form; 



