July, 1917.] GROWTH OF APPLE TREES. 27 



DAILY GROWTH. 



In addition to recording the annual growth made by the trees 

 in the various plots, we have also attempted to measure the daily 

 growth of the trees for three seasons, 1913, 1914 and 1916. The 

 intention was to try and obtain an index of the vigor of the trees 

 under different treatments, but since vigor is difficult to define 

 the results have not been satisfactory and no effort has been made 

 to utilize the data in that way. However, these data may be 

 worth recording since they are taken on a rather large scale and 

 represent three seasons which differed, especially as to rainfall. 

 The data represent gross field observations and can scarcely be 

 compared with the minutely accurate growth records to be found 

 in botanical literature where auxanometers are employed, which 

 would have been impossible in this case. 



During the season of 1913, 8 twigs from each plot or 80 twigs 

 in the orchard were measured daily; in 1914, 40 twigs per plot 

 or 400 twigs were measured; in 1916, 30 twigs per plot or 300 

 twigs were measured. This makes a total of 43,000 measure- 

 ments during three seasons on which this work is based. The 

 total number of 16ths that all these twigs grew in any plot in any 

 day is shown in Tables Nos. 9, 10 and 11. The plots are then 

 averaged and the graphs shown in Charts Nos. 7, 8 and 9 show 

 the average results of the orchard for each day. 



It will be seen that the amount of growth from day to day 

 varies considerably but these differences are less marked the 

 nearer the trees approach their resting period. We have at- 

 tempted to learn what external factor affected this growth to the 

 greatest degree, but of the factors under observation none cor- 

 relate exactly with the growth behavior. The growtb/seems to be 

 more or less erratic, behaving at times in the opposite way from 

 that expected. However, they follow somewhat closely the 

 curves of temperature but doubtless many factors so combine to 

 affect growth that no one factor can be clearly separated as the 

 governing one when the plants are not under controlled con- 

 ditions. These factors are exceedingly complex and preclude as 

 definite deductions as might have been hoped for. Neither the 

 curve of humidity or rainfall when considered apart from other 

 factors will correlate with the growth behavior. In Chart No. 9, 

 which shows the growth increments for 1916, it will be seen that 



