XV111 LIST OF ILLUSTRATIONS 



Figure Facing Page 



22. Percolation experiment. To show the relative pow- 

 ers of soils to take in water falling on the surface . 41 



23. Bottles used in place of the lamp chimneys in Figs. 



22 and 24 44 



24. Capillarity of soils. To show the relative powers 



of soils to take water from below .... 44 



25. Water-absorbing and water-holding powers of soils 45 



26. Capillary tubes. To show how water rises in small 

 tubes or is drawn into small spaces . . . -48 



27. Capillary plates 48 



28. A cone of soil to show capillarity 49 



29. To show the relative amounts of film-moisture held 



by coarse and fine soils 49 



30. To show the effect of a soil mulch . . . .56 



31. Soil temperature experiment . " . . . -57- 



32. Charts showing average temperature of a set of dry 

 and wet soils during a period of five days . . 60 



33. To show the value of organic matter . . .61 



34. Soy-bean roots, showing nodules or tubercles . . 64 



35. Garden-pea roots, showing tubercles or nodules . 65 



36. To show that seeds need water for germination . 72 



37. To show that seeds need air for germination . . 72 



38. To show that seeds need air for germination . . 73 



39. A seed-tester : two plates and a moist cloth . . 80 



40. A seed-tester : a plaster cast with cavities in the 



surface for small seeds 80 



41. Germinating corn-kernel and bean . . . .81 



42. To show how the bean-plant gets up ... 82 



43. To show how the corn-plant gets out of the soil . 82 



44. To show the use of cotyledons 83 



45. To show the use of the kernel to the young corn- 

 plant . . 86 



46. To show how deeply seeds should be planted . . 87 



47. Operations of seed-planting . . . .88 



48. A collection of planting machines . ... 89 



49. Spading-fork and spade . 92 



