x Table of Contents 



CHAPTER IV 



PAGES 



THE MEASUREMENT OF VARIATION 41-51 



The science of biometry , 41 type, 43 biometrical 

 expression of variability, 43 mode, 44 modal coeffi- 

 cient, 45 mean, 45 use of mean, 46 mathematical 

 expression of variability, 47 average deviation, 47 

 standard deviation, 48 coefficient of variability, 49 

 probable error, 50 use of statistical methods, 51. 



i 

 CHAPTER V 



MUTATIONS 52-91 



Evolutionary theories of Darwin and de Vries, 52 

 differences between fluctuating variations and mutations, 

 54 history of mutation, 55 history of the appear- 

 ance of double flowers, 56 de Vries' experiment with 

 cenotheras, 59 analytical table of seedlings (after de 

 Vries), 68 how the mutants were produced in the gar- 

 den, 71 mutating strains of O. Lamarkiana, 72 de 

 Vries' laws of mutability of the evening-primroses, 72 

 frequency of occurrence of mutations, 79 spontaneous 

 occurrence of new elementary species in the wild state, 

 80 spontaneous occurrence of new elementary species 

 and varieties under cultivation, 80 experimental study 

 of the origin of mutations, 84 experiments in the pro- 

 duction of double flowers, 86 what do new characters 

 come from, 90 can mutations be produced artificially, 

 90 economic significance of mutations, 90. 



CHAPTER VI 



THE PHILOSOPHY OF THE CROSSING OF PLANTS, CONSIDERED 

 IN REFERENCE TO THEIR IMPROVEMENT UNDER 



CULTIVATION 92-148 



The struggle fgr life, 92 survival of the most fit, 93 

 flexibility as an aid to survival, 93 causes of varia- 

 bility, 94 origin and function of sex, 95 effects of 



