STUDIES ON THE LIGNIN AND CELLULOSE OF woop. 49 
wholly delignified, but the summer wood was still lignified, 
and so far as could be noted showed very little effect from 
the boiling. The various cellulose and lignin tests were 
used and invariably indicated the same results. See plate 
rE: figure 2. Thus it seems to be proved that the lignin of 
the spring wood is held in combination less firmly than is 
that of the summer wood. This is probably due to the 
greater thickness of the walls in the summer wood, as the 
difference in thickness between the two parts of the ring 
was very marked as will be readily perceived on referring 
to plate 1, figure 2. The results of this test seem to furnish 
a clue as to the reason why certain of the wood rotting 
fungi disintegrate the walls of the spring wood while the 
summer wood of the same ring is apparently unaffected. 
Later tests with the various woods enumerated above 
have shown that what is true of the wood of Pinus palus- 
tris is also true of many others. The degree of different- 
iation between the two parts of the annual ring seems to 
be the controlling factor in the relative solubility of the 
lignin of those parts. In other words, those woods which 
have a decided difference between the spring and summer 
wood of the annual ring are almost sure to have the lignin 
extracted from the former quicker than it is from the lat- 
ter: and those woods which have but slight differences be- 
tween the two parts of the ring are apt to have the lignin 
extracted from all or nearly all of the ring at the same 
time. 
ENVIRONMENT AND LIGNIFICATION. 
Potter’s results may be accepted as true for the woods 
used by him but they cannot be taken as significant with 
respect to woods grown under all conditions. The above 
experiments have shown that there is a decided difference 
between the results obtained by him and those of the 
present tests. As is well known, there is a very great dif- 
ference in the environment of trees grown under different 
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