432 Variation of Water ae Trees and Shrubs, { May, 
If we next inquire into the relation which seasons bear to the 
contained water, we will observe that the percentage continually 
rises from the mid-winter period until spring, and that it again 
falls from the close of summer to the mid-winter period. The 
extreme variations, as exhibited in our figures, show between 
February and September a difference of 8.4 per cent for the 
youngest growth and 7.1 per cent for that which is older. 
MEAN HYDRATION OF WOODS, 
Determined at 100° C, 
Per cent water. || No. for average. 
Months. ae 
rst year. | 2d year. || rst year. | 2d year. 
POUR oe sess y 43-9 37 38 
March 47.2 | 44.8 59 60 
PTL OR SET 48.4 7 
September. 53-1 51.0 19 18 
laLa PEST ET RET yee 48.3 47.2 61 58 
49.0 ' 47.1 || 36.4 | 30-2 
Our figures also indicate that the maximum hydration of the 
tissues must occur either in September, or at some period inter- 
mediate to this month and April. By graphic representation of 
these results, it will become possible to determine with approxi- 
mate accuracy the true period at which this maximum is reached. 
The figures show that from February to April, the rate of per- 
~~ centage increase is much more rapid than the rate of percentage 
=- decrease from September to December, showing that the maxi- 
mum must fallynearer the former than the latter period. 
A properly constructed curve will show all of these relations. 
By reference to the accompanying diagrams it will be seen that 
= the curves for both young and old wood run nearly parallel, but 
~ that they tend to approach at their greatest depression, or the 
__ mid-winter period, and to more widely separate at their greatest 
altitude, during the spring period. It is also seen that from mid- 
-~ winter to spring, the curve rises rapidly, and reaches its greatest 
_ elevation about the last of May for the young wood, that which 
_is older possibly reaching its maximum a few days later. From 
this time on the curve descends at a more gradual rate until De 
cember, when it suddenly drops to its minimum depressio®, 
_ which evidently occurs in January. _ 
pre eer Ee ee eae oe eee 
