XI i 



CONTENTS 



CHAPTER IX. 

 THE AERATING OR VENTILATING SYSTEM. 



PAGE 



I. General Considerations 432 



11. Ventilating Spaces and Ventilating Tissues - - 434 



. I . Form of the A ir-spaces and Character of their Walls - - 434 

 13. The Structure of Ventilating Spaces and Ventilating Tissues, 



considered in Relation to certain Physiological Functions 436 



1. The Ventilating System in Relation to Respiration 436 



2. The Ventilating System in Relation to Photosynthesis 437 



3. The Ventilating System in Relation to Transpiration 438 



4. The Ventilating Arrangements of Marsh- and Water- 



plants 440 



5. Diaphragms and Internal Hairs .... 443 



III. The External Outlets of the Ventilating System - 445 



A. Stomata ---------- 445 



1. Structure and Mechanism of Stomata - - - 445 



2. The Importance of Stomata as Paths of Gaseous Inter- 



change ----- - - 456 



3. The Relations of External Conditions to the Move- 



ments of Stomata ------ 458 



4. The Structure of Stomata in Relation to Climatic 



and Edaphic Conditions - - 460 



5. The Stomata of Gymnosperms, Pteridophytes and 



Bryophytes ------- 468 



6. Subsidiary Cells - ... 471 



7. Distribution and Location of Stomata - - 472 



8. Loss or Change of Function on the Part of Stomata 474 



B. Lenticels ---------- 477 



C. The Pneuniathodes of Aerial Roots - - - 480 



1. The Pneuniathodes of Breathing-roots - - - 480 



2. The Pneuniathodes of other Aerial Roots - - - 481 

 IV. Ontogeny oe the Ventilating System - - - 483 



CHAPTER X. 



THE SECRETORY AND EXCRETORY" SYSTEMS. 

 I . ( ! uneral Considerations ------- 485 



