864 JOURNAL OF FORivSTRY 



The most striking fact brought out by the tables is the consistent 

 lead in height growth shown for the season of 1914. This is true of 

 the different ages in each series, independently, as well as in the aver- 

 ages. 1914 takes first rank in at least one case for all of the thirteen 

 ages included, with the exception of 11 and 13 years, which are in 

 third and second rank respectively. In no case does 1914 fall below 

 third rank and is third only twice out of twenty times. 



The relationships of the other seasons are also fairly constant, al- 

 though they show more variation than does 1914. The averages for 

 the two series show an identical ranking fOr each of the five seasons. 

 The individual ages check with the rank shown by the averages in a 

 sufficient number of cases to show a fair consistency throughout. 



Seasonal change in weather is clearly the dominant factor influenc- 

 ing rate in height growth between the ages included in the study. A 

 tabulation of the data in Tables i and 2 so as to group height growth 

 according to the year of the tree's age, rather than season, showed no 

 well-defined relation between year of age and relative height growth. 

 This holds true of the individual trees as well as the averages for each 

 age. It may reasonably be concluded, therefore, that the influence of 

 age at this period in the life of the tree is subordinate to changes in the 

 weather and physical factors which affect tree growth directly or 

 indirectly. 



The fact that height growth was so consistently greater in 191 4 than 

 in the two years just preceding or following raises the question as to 

 whether the season of 1914 dift'ered from the others in any marked 

 way. A detailed analysis of all the climatic records obtained during 

 this period is scarcely within the scope of this study. Furthermore, 

 the growth data are hardly intensive enough to warrant such a pro- 

 cedure. It is felt, however, that the relationships between growth and 

 climatic changes can be indicated, at least in a general way, by limiting 

 the comparison to three factors: air temperature, precipitation, and 

 cloudiness. 



Air temperature can, it is thought, be expressed in sufficient detail 

 for this study by using the mean monthly temperature — the mean of 

 the daily means of the maximum and minimum readings. Precipita- 

 tion needs a somewhat more detailed treatment, since its distribution 

 and the length of dry periods have an important influence upon growth. 

 The amount of sunshine can be indicated in a general way by the num- 

 ber of days in each month classified as "clear" (0.0 to 0.3 cloudy), 

 "partly cloudy" (0.4 to 0.7 cloudy), and "cloudy" (0.8 to i.O cloudy). 



Oeneral observations of larch indicate that height growth starts in 



