xiv Contents. 



PAGE 



17. Oenothera semilata 358 



18. Oenothera nanella (O. Laniarckiana nanella) 360 



Conception of Variety, 360; Dwarf Forms, 361; 

 Atavism, 2>^2) \ Constancy, 372 ; Compound Types, 375. 



C. The Inconstant Species 277 



19. Oenothera scintillans (Plate V) ^^yy 



Unfit Types, 381. 



20. Oenothera elUptica 393 



21. Oenothera sublinearis 399 



D. The Sterile Species 402 



22. Oenothera lata 402 



Units of the Characters, 402. 



2S. Incipient Species 416 



Sterility, 417; O. spatliulata, 419; O. fatua, 420; O. 

 sitbovata, 420. 



III. The Systematic Value of the New Species 425 



24. The Nature of the Boundaries Between Related Spe- 



cies 425 



Transgressive Variability, 426. 



25. Transgressive Variability 430 



Of the Petals, 433; Of the Fruits, 436. 



26. Oenothera Laniarckiana seringe 437 



Seeds, 437; Species of Ouagra, 438; Mutation Period 

 of O. biennis, 440; Diagnosis, 441 ; O. grandi flora, 441. 



27. Synopsis of the Characters of the New Species 444 



Fruits, 446-447; Analytical Tables, 448-454. 



28. Comparison of the Characters of the Old and New 



Species 454 



IV. On the Latent Capacity for Mutation 462 



29. Repeated Mutations Are the Result of the Same Inner 



Causes 462 



30. The Latent Inheritance of Other Characters in O. La- ■ 



marckiana 468 



Pitchers, 470; Tricotyly, 474; Fasciation, 476; Varie- 

 gation of Leaves, 480; Polymery, 481; Other Devia- 

 tions, 484. 



31. The Hypothesis of a Premutation Period 490 



Oenothera biennis, 495. 



V. Conclusion 497 



Ways to Look for Mutable Plants, 497; Cultures, 

 502; Intermediate Forms, 504; Species or Varieties, 

 506; Other Periods of Mutation, 510. 



