34 FORESTRY INVESTIGATIONS U. S. DEPARTMENT OF AGRICULTURE. 



Page. 

 FitJ. 1:2. Wood of beech, sycamore, birch 



13. Wood of maple.. 



14. AVoodofelm 



15. Wood of walnut 



16. Wood of cherry 



17. Variation of summer wood 



18. Variation of spccitic gravity 



19. Variation ofsniiiiiierwood, per cent 



20. Schematic representation of coniferous wood structure 



21. Cell endings in pine 



22. Cross section of normal and stunted growth i" longleaf pine 



L'li. Diagram showing arrangement of age classes 



24. Diagram showing comparative progress of yields of spruce, fir, pine, and beech .. 



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



L'i;. Tree classes: Classilication according to crown development 



27. Physiological importance of different parts of the tree; pathways of water and loud materials. 



28. Bad development of beech - 70 



29. Buds of maple 



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



31. Section through a 12-year-old stem of beech, showing manner of bud and limb formation. L'TI 



32. Section through a partly decayed knot in oak wood. . 



33. Development in and out of the forest 



34. Trees in and out of the forest 



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



:!ii. Scheme to illustrate the annual growth 271 



37. Oak tree grown in the open 275 



3H. Maple tree grown in the forest -'"' 



39. Showing plan of group system in regenerating a forest crop 2S9 



40. Appearance of regeneration by group method - 2!Mi 



1 1 . Method of layering to produce new stocks in coppice wood -*2 



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



43. Difference of temperature (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 0), 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, Lint/el Station, woods and open fields (W O) 320 



4*. Effects of litter on soil temperature (littered surface bare). (W 0) 321 



49. Difference of soil temperature, under sod and bare surface (sod bare). Becqnerel's observations 321 



50, 51, and 52. Forest air temperature, dill'ercnce 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 Friedrichsrode, 



Hagenan, 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 temperature 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. Tree-top temperature, differences (W 0) at Friedrichsrode, Eberswalde, St. Johann, 



Onrlsberg, and Schoo 32fi 



71, 72, 73, 74, and 75. Tree-top temperature differences, German stations (W O), Sonnenberg, Knrwien, 



Hagenau, and Nenuiath deciduous trees 327 



76. Tree-top temperature differences, German stations, evergreen trees 328 



77. Vertical temperature, gradient in woods, degrees Fahrenheit, for a hundred feet 328 



78. Vertical temperature gradients from observations above trees 328 



71*. Forest temperature differences above trees, from Fautrat's observations 328 



80. Evaporation and precipitation 329 



81. Monthly evaporation iu 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. Ratio of evaporation from water surface in fields and forest to precipitation 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 



