The soil should be deeply cultivated the first few years in order to make the roots strike deep into the ground, and afterward the soil should receive some surface cultivation every year. When there is danger of frost after the trees have bloomed, brushwood fires are lighted and a dense smoke is raised over the orchard by burning pots of crude oil. This smoke is helpful in preventing the formation of frost, and will often be the means of saving the crop. The other great causes of failure to grow large quantities of perfect fruit, if the varieties are well chosen, are plant diseases and damage by insects. The methods of their control are given in the chapter on Insects, and include principally the disposal of all decayed fruit, the raking up and burning of all leaves in infected orchards, arsenical and lime sprays, and, above all, such attention to pruning and cultivation as will keep the trees in good condition. Lastly, the keeping of bees in the orchard will pay well, not only for the honey they produce, but because they assist greatly in carrying the pollen from flower to flower, and so increasing the crop of fruit. REFERENCES Forests. Report National Conservation Commission. Forest Conservation, Papers and Discussions, Report Governor's Conference. Arbor Day, Forest Service Department of Agriculture Circular, 96. Tree Planting on Rural School Grounds. Forest Service Department of Agriculture Circular, 134. Practical Assistance to Tree Planters. Forest Service Department of Agriculture Circular, 22. How to Transplant Forest Trees. Forest Service Department of Agriculture Circular, 61. Forest Planting on Coal Lands. Forest Service Department of Agriculture Circular, 41. Forestry in the Public Schools. Forest Service Department of Agriculture Circular, 130. Primer of Forestry. (Pinchot). Forest Service Department of Agriculture Circular, 173. The Use of the National Forests. (Pinchot.) What Forestry Has Done. Forest Service Department of Agriculture Circular, 140. Forest Preservation and National Prosperity. Forest Service Department of Agriculture Circular, 35. Forest Planting and Farm Management. Forest Service Department of Agriculture Circular, 228. Facts and Figures Regarding our Forest Resources. Forest Service Department of Agriculture Circular, 11. Drain Upon the Forests. Forest Service Department of Agriculture Circular, 129. The Waning Hardwood Supply. Forest Service Department of Agriculture Circular, 129. Timber Supply of the United States. Forest Service Department of Agriculture Circular, 116. Forestry and the Lumber Supply. Forest Service Department of Agriculture Circular, 97. How to Cultivate and Care for Forests in Semi-arid Regions. Forest Service Department of Agriculture Circular, 54. Paper-making Materials and their Conservation. Bureau of Chemistry, 41. CHAPTER IV WATER