CONTENTS xv 



PAGE 



tion of the leaves evaporation of water. Function of the 

 stomata. Function of the vessels. Function of bordered pits. 

 Velocity of the sap. Purpose of the cork tissue. Movement 

 of nutrient substances formed by the leaf. Course of this move- 

 ment. Function of the sieve and latex-tubes. Causes of this 

 movement. Formation of stores of nutrient substances . .149 



VII 



GROWTH 



Nutrition and growth. Direction of growth in the root and 

 stem. Attraction by the earth. Turgidity of tissues. Mode 

 of action of gravity. Influence of light. Heliotropism. 

 Methods of measuring growth. Influence of temperature. 

 Thermotropism. 



Growth and multiplication of cells. Division of the nucleus. 

 The proximate effect of light on the growth of the cell-walls. 

 Effect of pressure on the form of cells. Growth mechanism of 

 cells. Possibility of hearing plants vegetate. The art of 

 experiment . . . . . . . 182 



VIII 



THE FLOWER 



Sexual and asexual reproduction of plants. The flower. Essential 

 parts of the flower ovule and pollen. Fertilisation. Fertilisa- 

 tion in the lowest plants. Adaptations securing the fertilisation 

 of flowering plants. 



Function of the so-called non-essential parts of a flower. Self- 

 fertilisation and cross-fertilisation. Co-operation of wind and 

 insects. Parts of the flower attracting insects. Special forms 

 of flowers adapted to cross-fertilisation by insects. The part 

 played by art in the production of cultivated varieties. Purpose 

 of selection. Insufficiency of physiological knowledge of the 

 nature of the sexual process . . . . . 225 



IX 



THE PLANT AND THE ANIMAL 



Current ideas as to the difference between plants and animals. 

 Capacity for movement in a plant. Microscopic movements : 

 of protoplasm, zoospores, and antherozoids. Movements of 

 organs in the highest plants under the influence of external 

 conditions (heat, light). Sensitive organs. Mechanism of these 

 movements. Spontaneously moving organs. Utility of various 

 movements. 



Similarity between the internal processes of movement in 



Elants and animals. Similarity in the processes of nutrition, 

 imilarity in the process of respiration. Respiration and fer- 

 mentation. Similarity between the phenomena of stimulation 



