.14 



Notes Upon the Rate of Tree Growth in Glacial Soils in 

 Northern Indiana. 



Stanley Coulter. 



The clearing of certain small timber areas near Lafayette in January 

 and February, 1906, gave an exceptional opportunity for studying the rate 

 of growth of certain native species of trees. The species occurring in suf- 

 ficient number to vi^arrant deductions were the white oak, red oak and 

 black walnut. Of the red oak forty -nine trees were examined ; of the white 

 oak, sixty, and of the black walnut, thirty-two. It was assumed that the 

 annual rings gave a fair indication of the age, despite the occasional forma- 

 tion of two rings in a single year, or the apparent suppression of an annual 

 ring because of exceptionally unfavorable conditions, which were recog- 

 nized as possible contingencies. In the forms examined neither of these 

 conditions were indicated, the growth in each case having apparently pro- 

 ceeded in an orderly and orthodox fashion. 



The measurements are the averages of the longest and shortest diam- 

 eters and were taken inside of the bark. Both the measurements and the 

 counting of the rings were made by four groups of students, insistence being 

 placed upon accuracy. In cases of discrepancy a recount or remeasurement, 

 or in some cases both-, was directed. The tables, therefore, may be con- 

 sidered as exceptionally accurate, each specimen having been independently 

 studied by four groups working on different days. 



The oaks, with but few exceptions, occurred on the highest levels, just 

 northwest of Purdue University. The general surface is rolling, with a 

 southeastern exposure, more or less interrui)ted by ravines formed by small 

 streams. Approximately the topographical conditions were the same. 



The soil in the area under consideration is relatively thin. It consists 

 of a few inches of humus made up of the usual forest material ; a few 

 inches (8-12) of a loam soil more or less alluvial in character, followed by 

 perhaps a foot of fairly heavy clay. Underlying this is the glacial drift, 

 extending downward from one hundred and ten to one hundred and twenty 

 feet to the bed of the river. The drift in this region is mainly sand and 



