VII.--SOIL TEMPERATURE 57 How soils are warmed 58 How soils lose heat How to check loss of heat 59 Conditions which influence soil temperature 60 Value of organic matter 61 VIII.--PLANT FOOD IN THE SOIL 63 IX.--SEEDS 70 Conditions necessary for sprouting 70 Seed testing 75 How the seeds come up 77 Use of cotyledons and endosperm 79 X.--SEED PLANTING 81 Depth of planting: Operation of planting Planting machines 81 Seed classification 85 Transplanting 87 XI.--SPADING AND PLOWING 90 Spading the soil 90 Plowing 91 Why we spade and plow 91 Parts of a plow 92 Characteristics of a good plow 95 The furrow slice 96 How deep to plow 96 "Breaking out the middles" 97 Ridging the land 98 Time to plow 98 Bare fallow 100 XII.--HARROWING AND ROLLING 101 Harrowing: Why we harrow Time to harrow 101 Types of harrows 102 Rolling 106 XIII.--LEAVES 108 Facts about leaves 108 The uses of leaves to plants: Transpiration Starch making Digestion of food Conditions necessary for leaf work 109 How the work of leaves is interfered with 115 XIV.--STEMS 120 What are stems for? 120 How the work of the stem may be interfered with 126