CONTENTS. 



Page. 



Introduction 7 



Dimorphism a phenomenon of alternative expression 8 



Abrupt changes of leaf forms in Hibiscus cannabinus 11 



Leaf forms of varieties of Hibiscus cannabinus 15 



Parallel leaf forms in cotton 17 



Two types of dimorphism of leaves in cotton 20 



Parallel leaf forms in okra 23 



Significance of parallelism in the study of heredity 27 



Relation of parallelism to classification 29 



Relation of dimorphism to mutation 32 



Relation of dimorphism to Mendelian inheritance ~ 36 



Different types of dimorphic specialization 38 



Relation of dimori)hism to sexual differentiation of plants 45 



Conclusions 50 



Description of plates 52 



Index 53 



221 5 



