EXPLANATION OF THE ILLUSTRATIONS 
Pirate Il. Sections of wood of submerged white pine stump. 
Fic. 1. Transverse section. Note the incipient degradation 
of the inner lamellae of the secondary wall of the tracheids, 
which shows compression wood, or “‘rotholz’” structure. The 
heavily stained layers between the degraded inner lamellae 
and the less heavily stained outer secondary wall are non- 
cellulosic layers of the secondary wall. »* 500. 
Kia. 2. Transverse section. The visibly intact layers of the 
cell wall consist of the intercellular substance, primary wall 
and the outer secondary wall. The lignin residues of the 
central and innermost layers of the secondary wall form a 
discrete cylinder in the lumen of each cell. In this section, 
as also in Fig. 8, the outermost secondary wall is unusually 
thick and appears to consist of more than one layer. Unde- 
lignified, stained with Ruthenium red. “800, 
Kia. 3. Same section shown in Fig. 2, except more highly 
magnified, Undelignified, stained with Ruthenium red, 
1400, 
Kia. 4. Transverse section showing varying extent of de- 
gradation of the secondary wall lamellae. ~ 800. 
Fic. 5. Transverse section of less degraded wood from inner 
parts of the stump. Note the varying degrees of degradation 
of the secondary wall and the retention of a structural frame- 
work of modified cell walls. Unstained preparation. 220. 
kia. 6. Same specimen as shown in Fig. 5, but from more 
extensively degraded wood. Unstained preparation, 530, 
