FOR WHOLE TREES. 29 



The age of yellow 'pine trees, which have grown tinder conditions 

 similar to those existing in Lassen County, can be determined from 

 outward appearances much closer than from height and diameter 

 measurements. Figs. 3 and 4 show that the immature trees merge into 

 a stage where the outward appearances are as much like the mature 

 as the immature, and finally into the ages where the characteristics of 

 the immature tree have vanished. The change in life, as this may be 

 termed, averages two hundred and sixty-five years. 



In Forest Service Bulletin No. 125, page 20, it is shown that the 

 maximum periodic annual growth of yellow pine is obtained at two 

 hundred and sixty years. That is, up till this age they have an accel- 

 erated growth, and lay on more wood each year than the year previous. 

 After two hundred and sixty years the growth is a retarded one, and 

 the volume of wood formed each year is a decreasing factor. 



It is interesting to note that the change in life occurs at two hundred 

 and sixty-five years, which is about the same age that the prime of life 

 is reached, as shown by a separate investigation. 



