18386, | Variation of Water in Trees and Shrubs. 427 
HYDRATION OF Woop FROM LIVING TREES. 
The specimens upon which the principal facts in this paper are 
- based, were collected as sections of living branches, representing 
on the one hand growth of two years, and on the other hand the 
growth of four years. For the obvious reason that the bark 
could not be properly separated from the wood with any degree 
of uniformity, it was left on in every case, so that in all the deter- 
minations here given the results show the combined percentage 
of water in wood and bark, Obviously this gives a result which 
differs materially from that which would be obtained if the wood 
and bark were considered separately. Also, while care was taken 
Not to collect specimens in which the dead bark was strongly 
developed, thus securing as great uniformity as possible, the very 
fact that the bark was present, as well as the certainty of its varia- 
bility in structural character, and thus also in hydration, as col- 
lected even from the same species at different seasons, rendered. 
certain variations in the results unavoidable. This will doubtless 
appear upon examination of specific cases, but error from this 
Source is reduced to a minimum in the aggregate, so that the 
mean results, in view of all the precautions taken, may doubtless 
be accepted as correct. 
From an examination of the following results it will appear 
that, comparing the young growth with the older wood, the per- 
centage of water is sometimes greater in one, sometimes greater 
in the other, conforming to structural peculiarities of the species 
| and the relative preponderance of more or less strongly hydrated 
tissue. The mean results, however, clearly show what we might 
infer upon theoretical grounds, viz., that in the youngest growth, 
as also in the sap wood, the percentage of water is higher by two 
- Per cent than in the older growth, where the heart wood is in 
relative excess. This is found to hold true in the mean results 
not only for each season but also for all seasons; in the former 
case, however, the disproportion showing a variation from 0.8 
Per cent to 3.3 per cent, 
