IIKIGIIT GROWTH AND WEATHER CONDITIONS 



863 



3. Total height. 



4. Distance between annual nodes of height growth on tlie main 

 axis for the past five seasons. 



Some difficulty was experienced in getting the complete growth for 

 the last season on some of the trees, since the extreme tips of larch 

 seedlings of this size are very weak and brittle. When the trees were 

 struck at the base with an ax, the sudden whipping of the tip through 

 the air caused the last few inches to be snapped off from about one- 

 third of the trees measured in May — 40 out of 112. Such trees with 

 broken tips were discarded in the November work. 



The tips were usually scattered beyond recovery, but enough were 

 recovered to permit of a close estimate of the average length of such 

 broken tips. There was little variation in the cases observed and it was 

 estimated that the length would average at least three inches. It would. 

 if anything, be a fraction over this; so that the figure is conservative. 

 Accordingly an addition of three inches was made to the 1916 height 

 growth of each of the trees with broken tips measured in the spring 

 series. 



The figures were first assembled by grouping the trees in one-inch 

 diameter classes. This was not found to be satisfactory, because of the 

 wide variation in ages of trees in each group. The effect of the natural 

 acceleration in height growth, which may be expected with increasing 

 age at this period in the life of the tree, was open to question and made 

 it difficult to draw fair conclusions as to the effect of climatic changes 

 in the different years. 



Because of this question as to the eft'ect of age, the trees were then 

 grouped by years of age as counted on the stump. While it is diffi- 

 cult in such work to determine the age in all cases to the exact year, 

 it is thought that the age of a majority of the trees was determined 

 correctly. Tables i and 2 summarize the data by age-groups. 



T.ARi.K 3. — Siiiiiiiuiry of Tables i and 2, SJioiciufi Rank in f [eight drowtli 



bv Seasons 



NoTK. — III case of a tic each season is vi'vcn the hi.uiher rank. 



