CONTENTS. 



Page 



Introduction 5 



Material and methods 9 



Variation in Ceratophyllum — general results 16 



Variation in different portions of the plant 27 



Variation in whorls on the main stem 28 



Variation in whorls on primary branches 36 



Variation in whorls on secondary branches 40 



Variation in whorls on tertiary and quaternary branches 45 



The relative size of the different portions of the plant, and the variation in 



this character 48 



Summary of results 54 



Relation between the number of leaves in the whorl and position on the plant 57 



Position regression in different portions of the plant — the first law of growth 



in Ceratophyllum 57 



Summary 88 



The correlation between differently situated whorls in respect to leaf-number ... 93 

 The variability of successively formed whorls— the second law of growth in 



Ceratophyllum 95 



Summary 106 



The relation of the presence of branches to the number of leaves in the whorl.... 109 



The position of branches 116 



Summary... 124 



General discussion of results 125 



General summary 133 



Literature cited 135 



3 



