EXPLANATION OF THE ILLUSTRATIONS 
Prare IIL, Fic. 1. Transverse section of wood of white pine 
stump. The section shows the cellulosic structural residue 
of degraded wood after extraction of lignin and lignin resi- 
dues by sodium chlorite treatment. Four tracheids possess 
visibly intact secondary walls. All other cells are repre- 
sented by walls consisting of intercellular substance, primary 
walls and outermost secondary walls. Stained with Rutheni- 
um red. 500, 
Fig, 2. Same specimen as Fig. 1. The cellulosic structural 
residue consists of intercellular substance, primary walls and 
outermost secondary walls. Evidence for the presence of a 
secondary wall residue is provided by the persisting first 
formed layers of the pit borders. Delignified section stained 
with Ruthenium red. * 870. 
Fic. 3. Same specimen as Fig. 1. Evidence that the cellu- 
losic residue consists in large part of the outermost layer of 
secondary wall is shown by the conspicuous remnants of the 
borders of bordered pit-pairs. Note the retention of the pit 
torus. Delignified, stained with Ruthenium red. » 870. 
Fie. 4. Tangential longitudinal section of a degraded late 
wood tracheid of white pine showing the granular lignin 
residue of the secondary wall, Note the remnants of the 
bordered pit-pairs. Such cell wall residues, when delignified 
and viewed in transverse section, show the organization rep- 
resented in Figs. 1, 2 and 8. * 500. 
Fic. 5. Bordered pit-pairs of a normal spruce tracheid. Com- 
pare the lamellae with those shown in Figs. 2 and 3.) 870. 
Fic. 6, Transverse section of “‘rotholz’’ of degraded white 
pine wood after treatment with 72 per cent sulphuric acid. 
The more heavily lignified primary walls and outer secondary 
walls yield a coherent structural residue comparable to that 
Ys 
shown in Plate II, Figs. 2 and 8.» 800. 
kia. 7. Same specimen as shown in Fig. 6, but from differ- 
ent portion of the stump. Section treated with 72 per cent 
sulphuric acid. Note the lignin residue of the pit borders 
and compare with the cellulosic residue of the pit borders 
shown in Fig. 8.0 500. 
