:;_> U'/.svo/i.s-m Academy of Sciences, Arts, and Letters. 



primary laterals ;md therefore exerts great pressure on the 



MM ;is |)ellefsen fl maintained. 



According i<> juiother group of investigators to be cited in the 

 discussion on the distribution of radial growth, excentric growth 

 is not dm- t<> an independent distribution of metabolized food and 

 the other factors commonly assumed to be effective. Both food 

 ;md irrowth are held to be distributed by the mechanical effects 

 of the environment in conjunction with the weight effects of the 

 structure in question or by the rate and path of the transpiration 

 current. 



N'ERAL FORM OP TREE-TRUNKS AND THE DISTRIBUTION OP 



RADIAL GROWTH. 



The distribution of radial growth on trees determines the form 

 of the stem and therefore its value as timber. Owing to the 

 economic importance of the shape of tree-trunks to the lumber- 

 ing industry foresters studied the distribution of radial growth 

 and its relation to the environment very extensively and have 

 collected many valuable data. Since the stem of a tree grown 

 in a far.' 1 ;,- <Vnse and uniform forest stand is relatively longer 

 and less tapering toward its upper end. free of branches and 

 therefore of more lumbering value than one grown in the open, 

 ^ in the environment of the two types have re- 

 much attention. 



?v">j-dlmger cl noted that the yearly increase in thickness on the 

 bra] and branched parts of stems grown in a forest dif- 



1 from each other. The annual distribution of radial growth 

 on the branch-bearing portion in a forest stand was found to be 

 similar to that on the entire trunk of a free-standing tree, which 

 bears branches nearly to its base. The thickness of the wood 

 rings in the branch-bearing part of stems was found to decrease 

 : : se upward. On the branchless portion of trunks in 

 dense forest stands the thickness of the recent rings was noticed 

 to have decreased from the branches downward although in some 

 cases the thickness of the new yearly growth remained practically 

 constant at the base of trunks. He thought that the presence 

 of el ',-d food was not the only requisite for the occurrence 



10 1. 0. 



81 1. c. 



