XIV CONTENTS. 



CHAPTEE IX. 



GEADATION OF ORGANS, &0. — CONCLUDING EEMAEKS. 



Gradation of organs, of the rostellum, of the pollen-masses — 

 Formation of the caudicle — Genealogical affinities — Secretion, 

 of nectar — Mechanism of the movement of the poUinia — Uses 

 of the petals — Production of seed — Importance of trifling 

 details of structure — Cause of the great diversity of structure in 

 the flowers of Orchids — Cause of the perfection of the con- 

 trivances — Summary on insect-agency — Nature abhors per- 

 petual self-fertilisation Page 247-293 



Index 294 



