xx CONTExNTS 



CHAPTER IV. THE AIR 



PAGES 

 I. Atmospheric Pressure. Growth under decreased or increased atmospheric pressure. 

 Wieler's and Jaccard's experiments. Atmospheric pressure on high mountains. 2. The Air 

 contained in Water. Solubility, composition, and diffusion of air in water. Devices for the 

 absorption and transport of oxygen in aquatic plants. Aerenchyma and other aerating tissues. 

 Pneumatophores. G. Karsten's and Greshoffs experiments. 3. The Wind. i. Wind and 

 Tree-groivth. Mechanical influences. Drying influences. Injurious effects of the latter on tree- 

 growth, ii. Wind and Reproduction. Anemophilous leaves. Their frequent presence in windy 

 localities. Anemophilous devices for dispersal of seeds. Importance in relation to distribution 

 at great distances apart. Treub's observations at Krakatoa ...... 69-82 



CHAPTER V. THE SOIL 



I. The Physical Properties of the Soil. Water capacity. Conveyance of water by capil- 

 larity. Permeability of various kinds of soil. 2. The Chemical Properties of Soils. Corre- 

 lations of physical and chemical properties. Effects of solutions on the absorption of water by 

 plants. Poisonous nature of concentrated solutions. Protective mechanism of plants against 

 increasing concentration of saline solutions in the cells. Various actions of salts on the structure 

 of plants. 3. Sodium Chloride, i. Presence and Function of Sodium Chloride in Plants. 

 Influence of sodium chloride on the structure of plants. Xerophilous character of halophytes. 

 Influence of sodium chloride on the production of proteids. Its influence on the structure of 

 fresh-water Algae, ii. Halophytes. Predilection for salt. Distribution of halophytes among 

 the families of plants. Origin of the halophilous mode of life. Inability to withstand competi- 

 tion inland. 4. Other easily soluble Salts. Alum : the solfataras. Saltpetre. 5. Serpen- 

 tine. Plants growing on serpentine. 6. Calamine. Calamine-plants. 7. Calcium 

 Carbonate, i. Action of Calcium Carbonate on the /Metabolism and Structure of Plants. 

 Poisonous effects on many plants. Power of accommodation to a calcareous soil. Experiments 

 and observations by Bonnier and others. Nature of the influence of lime on metabolism. Experi- 

 mental cultures by Fliche and Grandeau. ii. Character of the Flora on Calcareous Soil. Calciphilous 

 plants. Calciphobous or silicicolous plants. Instability of the relations of plants towards lime. 

 Thurmann's physical theory. Its refutation. Explanation of the difference between calcicolous 

 and silicicolous floras, and of their instability. Dissimilar relations to lime of closely allied 

 species. Parallel forms on soils rich and poor in lime. Nageli's theory. 8. Humus, i. The 

 Chemistry and Physics of Humus. Ash-constituents. Acid humus and mild humus. Leaf- 

 mould and peat. ii. The Mycorhiza. Endotrophic and ectotrophic mycorhiza. Thismia Aseroe 

 according to P. Groom. Saprophytes, iii. Chemical Diffe7'ences in Humus and the resulting 

 Flora. Dissimilar nature of the flora on different kinds of humus. Great exclusiveness of certain 

 species of plants. Plants growing on animal humus. 9. Living Substrata : Parasites. 

 Dependence on the chemical nature of the substratum ....... S3-1 1{ 



CHAPTER VI. ANIMALS 



1. Geographical Distribution of the Arrangements for Pollination, i. Omithophi- 

 lous Flozvcrs. Fritz Midler's and Belt's discovery of humming-bird flowers. Sun-birds as polli- 

 nators. Scott-Elliot's observations in Sonth Africa. Ornithophily in New Zealand. Feijoa, 

 a plant with sweet petals, ii. Entomophilous Flozvers. Different pollinators in lowlands and in 

 mountain ranges. Hermann Midler's observations. Decrease of entomophily in arctic countries. 

 Insular floras and their pollinators. Long- tubed Lepidopteron-flowers characteristic of the 

 tropics. Special adaptations. Yucca and its pollination by moths. Species of Bulbophyllum 

 near Singapore. 2. Plants and Ants. \. Ants as cultivators of Fungi. Leaf-cutting ants in 

 tropical America. Their nests and fungus-beds. Other ants that cultivate fungi, ii. Myrme- 

 cophily. Belt's discovery of myrmecophilous plants. Acacia cornigera and A. sphaerocephala. 

 Cecropia adenopus. Proof of the utility of ants as protectors of plants. Other plants with axial 

 habitations. Plants in which leaves produce the habitations. Extra-floral nectaries . 1 19-156 



