xiv TABLE OF CONTENTS 



FOURTH SECTION. 



MALFORMATIONS AND THEIR SIGNIFICANCE IN 



ORGANOGRAPHY. 



PAGE 



INTRODUCTION I77-I79 



Limitation of the notion of malformation 177 



I. SIGNIFICANCE OF MALFORMATIONS IN ORGANOGRAPHY . . . 179-183 



Malformations not without a rule ....... 179 



Abortion of sporangia in phyllody of stamens and carpels . . 179 



Such structure not atavistic, but diseased ...... 183 



II. ETIOLOGY OF MALFORMATIONS 184-200 



A. Many malformations can be inherited and may be latent until 



definite external conditions evoke them 184-187 



1. Fasciation 185 



2. Obligate torsion 186 



3. Sterility of Maize 1 86 



4. 'Gabler' 186 



5. Other cases 187 



B. Malformations caused by external conditions .... 187-200 



In Fungi 187 



In Algae 188 



In Spermaphyta 188 



Peloria. Peyritsch's observations 1 88 



Fasciation ........... 190 



Double leaves .......... 190 



Changes in flowers 191 



Effects of attack of fungi 192 



Effects of attack of insects ....... 193 



Double flowers 193 



Formation of galls 193 



III. SIGNIFICANCE OF MALFORMATIONS IN THE THEORY OF FORMATION OF 



ORGANS 200-202 



Sachs' hypothesis of material and form ....... 201 



Growth-enzymes ........... 202 



FIFTH SECTION. 



THE INFLUENCE OF CORRELATION AND EXTERNAL 

 FORMATIVE STIMULI UPON THE CONFIGURATION 



OF PLANTS. 

 INTRODUCTION 205 



I. CORRELATION 206 



Notion of correlation 206 



Quantitative and qualitative influence of correlation .... 207 



