410 The Botanical Gazette. (October, 
sue has been formed wood composed of smaller, much thicker 
walled cells is produced. 
In pine forests of recent growth the maximum thickness of 
the annual ring is found in the first ten years. In trees grown in 
the primeval forest, the maximum thickness is not reached 
until the one hundredth year; sometimes as late as the one 
hundred fiftieth or sixtieth. The thickness of the annual 
ring is greater in the upper part of the trunk than in the 
lower, excepting in trees grown in the open. This is due to 
two reasons: First, the action of the cambium begins three 
or four weeks earlier in the tops of closely growing pines than 
in the lower parts of the trunks, thus producing a greater 
number of cells above than below in the season; second, & 
the nourishment of the tree must pass from the top to all 
lower parts, the upper part is at all times supplied is 
wef, 
not 
ternal conditions, but also in different parts of the same tree. 5 
Of the timber from recently grown pine f 
paratively little transpiration, and wit ; 
late in the season, have valuable wood from th iokal 
Trees grown well up the sides of mountains or 1n wet 10 
ities have the best wood formed early. _ he outer 
The amount of water present decreas J 
part of the tree to the inner, with a su 
passing from sap-wood to heart-wood. 
of alburnum to duramen is not always the same o” 
sides of the sametree. There may be a differe : 
as ten annual rings. The percentage of shrinkage 0 oe 
wood of pine is much less than that of sap-w0o h cent: 
parison it is interesting to note that in the beech t yee fot 
age of shrinkage is the same for the old and yore hrinkage 
sap-wood and heart-wood, while in the oak the a : 
is much greater in the sap-wood. The st e to 
shrinkage in the heart-wood of pine and oak 1S i od, 
deposition of the material which characterizes heart-w"™ 
the micellar interstices of its cell walls. : 
A difference in size of trees of the sam 
related to the difference in size of the 
them 
e age is VOY © eg 
elements COMr 
