LIST OF ILLUSTRATIONS 



1. Variation in heads of timothy 3 



2. Two seedling timothy plants, growing side by side, showing 



a common kind and degree of difference ... 4 



3. A productive timothy plant ....... 5 



4. A timothy plant that runs much to seed . . . . 6 



5. A timothy plant that runs almost wholly to leaf ... 7 



6. Couch or quack grass, showing means of asexual propaga- 



tion by underground root stalks 13 



7. Orange hawkweed ........ 32 



8. A frequency curve illustrating the distribution, of the height 



of the pea plants ........ 42 



9. Variations in statures of CEnothera nanella, a mutant, and 



(Enothera Lamarkiana, its parent 53 



10. Variations in the amount of sugar in 40,000 beets . . 64 



11. Chelidonium majus ........ 55 



12. Chelidonium laciniatum . . . . .56 



13. Anemone coronaria, single-flowered form .... 57 



14. Anemone coronaria, semi-double-flowered form ... 57 



15. Anemone coronaria var. florepleno ..... 58 



16. Hugo de Vries . .59 



17. CEnothera Lamarkiana and (Enothera nanella in bloom . 60 



18. CEnothera Lamarkiana. Curve exhibiting variations in the 



length of fruits of 568 plants 61 



1 9. CEnothera lata CEnothera Lamarkiana CEnothera nanella 63 



20. A, spike with almost ripe fruits of CEnothera gigas, a mutant 



species; B, the same of CEnothera Lamarkiana, its 



parent form 66 



21. The cage in Professor de Vries' experiment garden, showing 



corn and various species of CEnothera . . . .70 

 xv 



