Xvi CONTENTS. 



PAGE 



Relation of Transpiration -to Absorption 279 



Adaptations of Plants to Dry Climates ." . . 280 



Chief Effects of Transpiration upon the Plant 281 



Influence of Transpiration upon Amount of Moisture in the Air , . 281 



Effect of Transpiration upon the Soil ........ . . 283 



Do Leaves absorb Aqueous Vapor ? 283 



CHAPTER X. 



ASSIMILATION. 



APPROPRIATION OF CARBON, OR ASSIMILATION PROPER 285 



Conditions of Assimilation . 285 



Assimilating System of the Plant . 285 



Chlorophyll 286 



Origin of the Granules 287 



Occurrence of the Granules 288 



Structure of the Granules 



The Chlorophyll Pigment, and its Extraction . . , 



Spectrum of Chlorophyll 292 



Fluorescence of Chlorophyll . 294 



Plants devoid of Chlorophyll 294 



" Colored " Plants 294 



Etiolation . . . . 295 



Chlorosis 297 



Autumnal Changes of Color . . , - . 297 



Chlorophyll in Evergreen Leaves . . 298 



The Raw Materials required for Assimilation, and their Reception 



by the Assimilating Organs 299 



Absorption of Carbonic Acid by Water Plants 299 



Absorption of Carbonic Acid by Land Plants 300 



Diffusion of Gases 301 



Passage of Gases through Epidermis free from Stomata 302 



.Passage of Gases through Stomata 303 



Composition of the Atmosphere 303 



Practical Study of Assimilation . 305 



Energy 307 



Classification of the Rays of the Spectrum 308 



The Depth to which Light can penetrate Green Tissues . . . . 309 



Quality of Light which penetrates the Tissues of a Leaf . 309 



Effect of Colored Light upon Assimilation 310 



Measurement of the Amount of Assimilation 312 



Engelmann's Method 314 



Effect of Artificial Light upon Assimilation 316 



Relations of Temperature to Assimilation 316 



Effect upon Assimilation of Variations in the Amount of Carbonic 



Acid furnished the Plant 318 



