34 FORESTRY INVESTIGATIONS U. S. DEPARTMENT OF AGRICULTURE. 



Fig. 12. Wood of beech, sycamore, lurch 105 



13. Wood of maple 105 



14. Wood of elm 105 



15. Wood of walnut 106 



16. Wood of chciry 106 



17. Variation of summervrood 109 



IS. Variation of specific gravity 110 



19. Variation ol summerwood, per cent Ill 



20. Schematic representation of coniferous wood structure 112 



21. Cell endings in pine 112 



22. Cross section of normal and stunted growth in longleaf pine 113 



23. Diagram showing arrangement of age classes 213 



24. Diagiam showing comparative progiess of yields of spruce, fir, pine, and beech 214 



25. Iron dibble used in setting out small pine seedlings 247 



26. Tree clashes: Classification accoiding to ciown development 253 



27. Physiological importance of different parts of the tiee; pathways of water and food materials 269 



28. Bud development of beech 270 



29. Buds of maple 270 



30. Dormant bud on a 12-year-old branch of beech 271 



31. Section through a 12-year-old stem of beech, shov, ing manner of bud and limb formation 271 



32. Section through a partly deca^ ed knot in oak wood 271 



33. Development in and out of the forest 272 



31. Trees in and out of the forest 273 



35. Sections of logs showing the relative development of knots 274 



36. Scheme to illustrate the annual growth 271 



37. Oak tree grown in the open 275 



38. Maple tree grown in the forest 275 



39. Showing plan of group system in regenerating a forest crop 289 



40. Appearance of regeneration by group method 290 



41. Method of layering to pioduce new stocks in coppice wood 292 



42. Differences of mean annual temperatures of soil (W — O) 318 



43. Difference of temperatuie ( W — O) at the depth of 4 feet 319 



44. Differences of soil temperature (woods and open fields). Comparison of deciduous and evergreen trees 



(W— O) 319 



45. Difference of soil temperature ( W — O), all stations—German observatories 320 



46. Differences of soil temperature (woods and open fields). Comparison of elevations above sea level 



(W— O) 320 



47. Differences of temperature for young trees, Lintzel Station, woods and open fields (W — O) 320 



48. Effects of litter on soil temperature (Jittered surface — bare). (W — O) 321 



49. Difiereuce of soil temperatme, under sod and baie surface (sod — bare). Becquerel's observations 321 



50. 51, and 52. Forest air temperature, difference of woods and open fields (W— O), deciduous trees, 



evergreen trees, and young forest (Lintzel) 321 



53. Forest air temperature differences, W — O. German stations 322 



54, 55, 56, 57, and 58. Forest air temperature differences, woods and open fields (W — O), at Friedrichbrode, 



Hagenau, Sonnenberg, Eberswalde, Schoo, Marienthal, Hadersleben, and average 323 



59, 60, 61, 62, and 63. Forest air temperature differences, woods and open fields (W — O) at Marienthal, 



Hadersleden, elevated stations, near sea level— average 324 



64. Forest air temperatui e differences for the year at height of the tree top ( W — O) 325 



65. Average differences of tree-top temperature, sixteen German stations ( W— O) 325 



66. 67, 68, 69, and 70. Tiee-top temperatuie, differences (W — O) at Friedrichsiode, Eberswalde, St. Johann, 



Carlsberg, and Schoo 326 



71, 72, 73, 74, and 75. Tree-top temperature differences, German stations (W— O), Sonuenberg, Kurwien, 



Hagenau, and Neumath— deciduous trees 327 



76. Tree-fop temperature differences, Geiman stations, evergreen trees 328 



77. Vertical temperature, gradient in v\ oods, degrees Fahienheit, for a hundred feet 328 



78. Vertii al temperature giadients from observations abo\ e trees 328 



79. Forest temperatuie differences above trees, fiom Fautrat's observations 328 



80. Evaporation and precipitation 329 



81. Monthly evaporation m the fields (upper curve) and woods (lower curve), in inches 329 



82. Percentage of evaporation in the woods as compared with that in open fields 329 



83. Eatio of evaporation from water surface in fields and forest to piecipitation 329 



84. Percentage of evaporation in woods to that in the open air 329 



85. Method of chemical analysis of turpentine 336 



86. Method of distillation of turpentine 337 



87. Distribution of turpentine in trees 339 



