412 The Botanical Gazette. [October 
been more rapid in the upper part of the tree than in the — 
lower. From the beginning of August to the middle starch — 
is entirely wanting in the phloem of the branches. In the 
phloem of the stem only traces of it are found in the outet 
part. It is assumed that the starch has been withdrawn from — 
the phloem a second time to be used in the growth of the — 
phloem itself. Not until the beginning of September has the — 
accumulation of reserve food begun again in the phloem, , 
then only in the lower part of the stem. As late as the 30th 
of September the bark of the 1—2-year-old twigs is still free 
of starch, although it is abundantly supplied with it by the — 
end of October. In December the starch has been changed 
into sugar and oil. x 
The amount of water in oak wood taken from different parts _ 
of the same tree varies considerably. It is very abundant, as. 
a rule, in the outer layers of sap-wood; less so in the innet — 
layers; while the outer portion of the heart-wood a 
ing amount — 
the sap-wood. The wood of the root-shaft contains more 
water than that of any other part of the tree. By pike 
roots, however, seem to be poor in water. There 1s a io 
crease in the amount of water present in passing from eh 
base of the tree toward the crown. This decrease continu 
in very old trees to the ends of the twigs. A 
the iciniten is continued to the upper end of bole, but from 
here to the extremities of the twigs, there 1s 4 
crease. In perfectly air-dry oak wood, to every I 
of the wood substance there are 19 to 20 volumes of 
tion water. 
ternal conditions. The smaller roots, which eit 
perform any mechanical function for th 
a limited degree, contain no trace of m 
mechanical tissue that they furnish we a 
wood of the tree. In these places strong w00 che th 
for resisting the forceof winds. If forany reasonh™™ 
