46 Wisconsin Academy of Sciences, Arts, and Letters. 



other variety since they were to be removed after the Baldwins 

 had attained some size. Nearly all of the Baldwin trees had the 

 bark injured about a decimeter above ground during the winter 

 of 1910-11, and over 80% had practically entire girdles of loos- 

 ened or injured bark so that they had become worthless, while 

 none of the low headed Ben Davis trees were affected. In an- 

 other case 91 bark injury resulted high up the trunks of bearing 

 trees after a severe pruning. 



It was also found that radial growth is often very late in thick 

 callus rolls about old cankers and sometimes on the under side, 

 or on the concave side of crooks in horizontal branches. The 

 bases of water sprouts or adventitious ascending shoots that arise 

 on the larger branches of excessively pruned young apple trees 

 also undergo very late radial growth and apparently for that 

 reason are winter-injured in those regions ; as in some cases dis- 

 cussed on pages 40 to 42 of the above cited paper on crown-rot. 

 Very similar observations regarding the distribution of winter- 

 injury in the bark of trees had been made by Nordlinger. 92 He 

 also assumed that such places are injured because of their late 

 growth. 



The reasons for the occurrence of late radial growth at certain 

 places on trees are doubtless the same as those underlying the 

 general distribution of excentric growth, and have not been fully 

 determined as yet. It seems, however, that the re-distribution of 

 bark pressure incident to radial growth, the distribution of 

 elaborated food, the location of the channels for water conduc- 

 tion, and the gravity-wind pressure effects advocated as factors 

 which regulate the distribution of radial growth, may afford at 

 least a partial explanation of the localization of late growth after 

 they have been submitted to a more careful quantitative study. 



WHAT CAUSES RADIAL GEOWTH TO APPEAE AS " ANNUAL" RINGS. 



The general distribution of radial growth in trees has also an 

 indirect relation to the development of "annual" rings in that 

 the proportion of spring and summer wood of a ring at any level 

 of a stem is doubtless dependent upon the comparative distribu- 



n 1. c. p. 24-27. 



" Ndrdlinger, H. Die September-Froste 1877 tind der Astwnrzel- 

 schaden (Astwurzelkrebs) an Baumen. Centbl. Gesam. Forstw. 4:489- 

 90. 1878. 



