Contents. xiii 



PART II. 



THE ORIGIN OF ELEMENTARY SPECIES IN THE GENUS 



OENOTHERA. 



PAGE 



The Pedigree Families 217 



1. Oenothera Lamar ckiana, a Mutating Plant (Plate I) . . 217 



2. The Lamarckiana-Family 221 



Pedigree, 224. 



3. The Mutations in the Lamarckiana-Family 226 



O. gigas, 226; O. Albida, 229; O. ruhrinervis, 230; 

 O. oblonga, 234; O. nanella, 235 ; O. lata, 239; O. scin- 

 tillans, 243. 



4. The Laws of Mutation 247 



Sudden Appearance, 248; Constancy, 249; Elemen- 

 tary Species, 251; Indefinite Direction of the Muta- 

 tions, 255. 



5. A Branch of the Lamarckiana-Family 259 



Pedigree, 262. 



6. The Laevifolia-Family 265 



Original Locality, 266; Pedigree, 273. 



7. Two Lata-Families ( Plate IV) 27S 



O. ruhrinervis and O. oblonga from O. lata, 283 ; 

 Pedigrees, 285, 288. 



8. Mutations in Other Families 289 



Characters of the Leaves, 293-295 ; ]\Iutants from 

 Crosses, 298-299. 



9. Mutations in Nature 300 



Beginning of the Mutation Period, 306. 



II. The Origin of Each New Species Cosidered Separately. 308 



A. The Two Older Species 308 



10. Oenothera laevifolia 308 



Crumples on the Leaves, 310. 



11. Oenothera brevistylis 315 



B. The Constant New Species 318 



12. Oenothera gigas (Plate II) 318 



13. Oenothera rubrinervis 3^7 



Units of the Characters, 328. 



14. Oenothera oblonga (Plate VI) 337 



Mutation Coefficients, 337. 



15. Oenothera albida (Plates III and IV) 349 



16. Oenothera leptocarpa 353 



