XV.--FLOWERS 128 Function of flowers 128 Parts of flowers 129 Functions of the parts: Cross pollination 130 Value of a knowledge of the flowers 134 Fruit 136 PART II SOIL FERTILITY AS AFFECTED BY FARM OPERATIONS AND FARM PRACTICES Chapter Page XVI.--A FERTILE SOIL 141 Physical properties: Power to absorb and hold water Power of ventilation Power to absorb and hold heat 142 Biological properties 143 Nitrogen-fixing germs 144 Nitrifying germs 145 Denitrifying germs 147 Chemical properties: Nitrogen in the soil Phosphoric acid in the soil Potash in the soil Lime in the soil Great importance of physical properties 147 Maintenance of fertility 150 XVII.--SOIL WATER 151 Importance of soil water 151 Necessity of soil water 151 Sources and forms of soil water 153 Too much water 154 Not enough water 154 Loss of soil water 155 How some farm operations influence soil water 156 Hoeing, raking, harrowing and cultivating 158 Manures and soil water 159 Methods of cropping and soil water 159 Selection of crops with reference to soil water 160 XVIII.--THE AFTER-CULTIVATION OF CROPS 164 Loss of water by evaporation 164 Loss of water through weeds 165 Saving the water 165 Time to cultivate 166 Tools for after-cultivation 167 Hilling and ridging 169