Grossenbacher — Radial Growth in Trees. 33 



of radial growth in any particular region of a tree-trunk for the 

 reason that the radial growth maxima in dense stands move up- 

 ward more rapidly than would be demanded by the reduction in 

 metabolized food. 



Sanio 62 noted that in case of a dwarfed fourteen-year-old sap- 

 ling of Fraxinus excelsior growing in a swamp the spring wood 

 was for the most part very thin and usually had but a single 

 row of vessels while in some parts of the stem the rings were de- 

 void of vessels. He thought it likely that spring growth had 

 been wholly omitted at such places and that the ring there con- 

 tained only summer-growth wood. 



R. Hartig 63 has probably published more on the general dis- 

 tribution of radial growth than any other investigator. From 

 a study of overtopped pines and spruces between 20 to 30 years 

 old, he found that the rings became thinner from the branched 

 top downward and that in some cases as many as seven rings had 

 been entirely omitted on the lower part of stems. When rings 

 had been omitted during a series of years the lower edges of 

 the new rings or wood-sheaths were found to have receded farther 

 from the base each year. In another paper he 64 called attention 

 to the fact that in overtopped trees a reduction occurs in the 

 yearly amount of wood produced from the branches downward. 



In general a stem is said to have three more or less distinct 

 growth regions in each of which a typical distribution occurs. 65 

 In the main axis of the branched top the cross sectional area of 

 the growth rings is said to increase from above downward. The 

 rings on the branchless shaft also increased in thickness from 

 the branches downward in trees having a well developed top, 

 but as stated above, the reverse was found true of a dominated 

 tree with a small top. 



A more detailed study of the distribution of radial growth was 

 carried out by Hammerle 66 in connection with his observations 



•" Hammerle, J. Zur Organization von Acer Pseudoplatanus: Biblio. 

 Bot. 50:1-101. 1900. 



" a Sanio, K. Verleichende Untersuchungen fiber die Zusammenset- 

 zung des Holzkorpers. Bot. Zeit. 21:391-99. 1863. 



" Hartig, R. Das Aussetzen der Jahresringe bei unterdrtickten Stam- 

 men. Zeit. Forst.-u. Jagdwesen. 1:471-76. 1869. 



. " Hartig, R. Zur Lehre vom Dickenwachsthum der "Waldbaume. 

 Bot. Zeit. 28:505-13; '521-29. 1870. 



> •* Hartig, R. Ueber den Entwicklungsgang der Fichte im Geschlos- 

 senen Bestande nach hone, Form und Inhalt. Forst. Naturwiss. Zeit. 

 1:169-85. 1892. 



3— S. A. 



