xii TABLE OF CONTENTS 



PAGE 



IV. RELATIONSHIPS OF SYMMETRY- OF LEAVES 114-128 



Asymmetry in dorsiventral leaves TI 4 



1. Cotyledons ... I! S 



2. Foliage-leaves 



A. Asymmetry of entire leaves 116-122 



Relation to direction of leaf .... 116 



Leaves of Begonia . 1 17 



Inequality of sides of compound leaves . . 120 



B. Asymmetry and unequal size of leaflets . . 122-128 



a. Asymmetry of leaflets 122 



Not caused by gravity . 123 



Relations to light ... 124 



Asymmetry of stipules . 125 



b. Leaflets of unequal size . 126 



Interruptedly pinnate leaves . 127 



V. RELATIONSHIPS OF SYMMETRY OF FLOWERS AND INFLORESCENCES . 128-138 



1. Flowers . 128-134 



Radial and dorsiventral flowers .... 128 



Asymmetry of dorsiventral flowers . . 128 



Relationship of symmetry of flower to inflorescence . . 128 



Flowers which become dorsiventral in development . . 129 



Flowers which are dorsiventral from the beginning . . 130 



a. Essentially 'zygomorphous' flowers ..... 130 



b. Unessentially 'zygomorphous' flowers . . . 130 

 Origin of dorsiventrality in flowers ... 131 



2. Inflorescences . 134-138 



Radial and dorsiventral ....... 134 



Inflorescences which become dorsiventral in development . . 134 



Inflorescences which are dorsiventral from the beginning . 134 



Biological relationships of inflorescences 134 



1. In anemophilous plants 134 



2. In entomophilous plants 135 



THIRD SECTION. 



DIFFERENCES IN THE FORMATION OF ORGANS AT 



DIFFERENT DEVELOPMENTAL STAGES. 



JUVENILE FORMS. 



INTRODUCTION . . 141-148 



Duration of development depends upon internal and external causes 141 

 Limitation of development in severed cells or cell-masses often a 



consequence of their origination 141 



Unfavourable external conditions often shorten the development 142 



Homoblastic and heteroblastic development = 143 



