Periodical Literature 531 



trees of three or of five stem classes. That the diameter is largely 

 the maker of value has long been demonstrated. The problem 

 resolves itself, then, to ascertain the time for the production of 

 certain diameter or ring width on a certain cross section. 



In general, the period from thicket to middle pole age is the 

 time of most vigorous growth and widest annual rings. Later, 

 the ring width in close stand declines, but with good thinning 

 practice the differences between different age classes become small. 

 It is also to be noted that the mean stems of the stand from one 

 age class to another grow in greater proportion than their annual 

 rings predicate, because, due to the exclusion of suppressed mem- 

 bers, they get into higher stem classes. Taking account of these 

 two disturbing influences, we may assume that the differences of 

 the average ring width of mean stems of stands are for a long time 

 so little that they can be neglected. 



The steadiness of the increment of the mean stems appears from 

 the ring width for different age classes figured from the yield tables. 



Age: 60 80 100 120 140 



Beech (Grundner) 1.5 1.6 1.6 1.6 1.5 mm 



(Schwappach) 1.1 1.3 1.3 1.2 1.2 " 



i< 



Spruce {Gnindner) 1.8 1.7 1.7 1.6 . 



(Schwappach) 1.7 1.6 1.5 1.4 . 



Ptnc (Grundner) 1.7 1.7 1.7 1.6 1.6 " 



(Schwappach) 1.5 1.5 1.4 1.4 1.3 " 



The author then on the basis of Bavarian statistics brings data 

 for showing the actual value increments determined for oak, beech, 

 pine and spruce. 



In two oak districts, where trees are divided into five size 

 classes, middle diameters differing by 4 inches, the following prices 

 were obtained per cubic foot, without bark, cut in the woods: 



Class V IV III II I 



Diameter Average 10 14 18 22 26 



Cents 18.4 35.4 51.6 64.4 83 



Differences 17 16.2 12.8 18.6 



Percent 64 37 24 24 



To translate these price relations into time relations of their 

 production in the forest certain assimiptions must be made. If 

 the average height is taken as 100 feet, the clear boles under 

 proper management will be about 30 feet, and if a height of 15 



