indicates that gradual hydrolysis of the cellulosic matrix 
of the cell walls has proceeded at a rather uniform rate, 
the degradative changes first affecting the peripheral 
zone and slowly extending inward. 
Ultimate complete degradation of the cellulosic frame- 
work of the wood cell wall may be delayed for enor- 
mously longer periods than have elapsed since the be- 
ginning of post-glacial time (Mitchell and Ritter, 1934; 
Jurasky, 1988; Barghoorn and Bailey, 1938). Recent 
extensive studies of lignites of Tertiary age show that 
in various genera of hardwood trees the lignitized wood 
retains from two and one half to six per cent of its origi- 
nal carbohydrate fraction, the major constituent of this 
fraction being degraded cellulose. In the same deposit 
lignitized fruits and seeds may show retention of as much 
as 45 to 50 per cent of their original carbohydrate frac- 
tion, predominantly cellulose.’ 
One aspect of the general problem which is of consid- 
erable theoretical, if not practical, interest is that dealing 
with the causes of selective retention of cellulose in cer- 
tain lamellae of the cell wall. Two possible explanations 
for the selective degradation of cellulose are immediately 
apparent: (1) the presence in the cellulosic matrix of 
substances which effectively retard the hydrolysis (either 
microbiological or chemical) of cellulose; and (2) actual 
chemical differences in the cellulosic framework of the 
more resistant lamellae of the cell wall. 
The first of these possible explanations finds much sup- 
port from various observations and lines of evidence. For 
example, it has been established quantitatively by sev- 
eral investigators that the degree of lignification corre- 
lates with resistance to decay in wood and other woody 
tissues (Waksman and Cordon, 1986; Olson, Peterson 
' Unpublished data from analyses of the Brandon lignite of Brandon, 
Vermont. 
[ 11 ] 
