99 CHRISTISON—OBSERVATIONS ON 
2. Three periods of two months eath—Dividing the growing 
season into equal first, middle, and last periods, it comes out that 
the girth-increase in the first was less than in the last on the 
average, though not in the year 1893, but that both, as a matter 
of course, were much below the middle, in which nearly three- 
fifths of the whole seasonal increase took place, whereas the first 
period ciaimed only a sixth and the last one quarter of the 
whole. 
First. Middle. Last, 
1802S: oie ae 2 11°9 64°9 23°2 
BEL So er eee Yas 23°7 55°5 20°8 
1804, oe eee cas 178 59°7 22°'5 
1895, ... ax “as =e 16°7 54:0 29°3 
Average, fe se — 17-5 58:5 24:0 
The annual variation or range was much greater in the first 
period than in the others, being in the proportion of two to one, 
whereas in the last it was as three to two, and in the middle 
period as six to five. The excessive variation of the first period is 
no doubt due to the great irregularity in the arrival of spring in 
our climate. In the two midsummer months growth is well 
established, and therefore is much steadier. In the two autumn 
months the girth-increase begins to die away, and therefore 
again becomes more irregular, but probably it is less affected by 
climatic variations than in the spring-months, and hence its 
range is less. . 
3. Sex periods of one month each-—The Table of monthly per- 
centages shows that the first and second months are exceeded 
by the last and second last months respectively, but only on an 
[ PERCENTAGE. 
