MICHIGAN ACADEMY OF SCIENCE. 221 



uating the quality of the site under discussion. The average annual growth 

 of Norway spnice for the first fifteen years (this period is taken from the 

 time of planting) on sites of the poorest quality used for spruce is 0.23 of a 

 foot. Our growth lias been 0.19, which shows that these poorest spots are 

 somewhat lower in quality than the poorest spruce sites of Europe. Using 

 the pine figures in the same way shows that these same spots correspond almost 

 exactly to the medium, or average, quality of sites used abroad for Scotch 

 pine. 



Taking the growth of the spruce for this plantation as a whole, however, 

 we find that it is nearly equal to that of sites of medium quality. If Scotch 

 pine had been planted over this whole area, it doubtless would have made 

 even better growth than the average of the best pine sites of Europe. Speaking 

 technically, this means that by growing spruce on this area we are working 

 with Site II ; in pine it would be Site I. The European growth figures for 

 these sites at the end of 120 years are : 



Scotch Pine. Average diameter, 15.4 inches. 



Average height, 103 feet. 

 Norway Spruce. Average diameter, 11.5 inches. 



Average height, 84 feet. 



In 1924, at the time of the next measurements, we shall be able to predict 

 more definitely the probable growth of the white and western yellow pines, 

 a thing that we are unable to do at present because of their habit of starting 

 more slowly than the Scotch pine. 



University of Michigan. 



