CONTENTS. 



CHAPTER I. 



THE ORIGIN OF PETALS . 



CHAPTER II. 



GENERAL LAW OF PROGRESSIVE COLOURATION 17 



CHAPTER III. 



VARIEGATION 6l 



CHAPTER IV. 



RELAPSE AND RETROGRESSION 71 



CHAPTER V. 



DEGENERATION 91 



CHAPTER VI. 



MISCELLANEOUS . IIO 



