Barghoorn, 1944). Early stages of this restricted break- 
down of the cellulosic matrix are illustrated in Plate IV, 
Figs. 1 and 2, showing the invasion of wood by fungal 
hyphae. Similar in nature are the effects of certain brown 
rots on the degradation of wood. These are shown, per- 
haps more diagrammatically in Plate IV, Figs. 8 to 6. 
In some cases the entire secondary wall (with the excep- 
tion of the tenuous outer layer) is completely removed, 
leaving a structural residue consisting of five layered 
‘‘membranes’’ similar in composition to those previously 
described from wood degraded under anaerobic condi- 
tions (compare Plate III, Figs. 1 and 8 with Plate IV, 
Figs. 3, 4, 5 and 6). 
All of this evidence indicates that the deterioration of 
wood is primarily a process of removal of cellulose, the 
rate of loss being, in many cases, significantly correlated 
with the degree of lignification or the protection of cel- 
lulose by other substances. 
A fundamental exception to this relatively simple ex- 
planation, however, may be determined by an anatomical 
study of plant remains extracted from peats. In defloc- 
culated, and subsequently delignified (‘‘dehumified’’), 
samples of fibrous peats innumerable delicate plant frag- 
ments are often released. In grass and sedge peats these 
fragments are most commonly cellulosic epidermal resi- 
dues of roots and rhizomes. Microscopic examination 
often reveals preservation of even the most delicate epi- 
dermal structures such as root hairs, root cap cells and 
epidermal papillae (Plate VI, Figs. 1 to 6). Although 
these tenuous residues of roots have retained minute ana- 
tomical features in certain parts, they are devoid of their 
thick walled fibrous or conductive tissues (Plate VI, 
Figs. 1 and 2). However, in undelignified preparations 
of comparable roots there may be found degraded rem- 
nants of the originally thick walled conducting tissues 
[ 13 ] 
