EXPLANATION OF THE ILLUSTRATION 
Plate 3. Figures 1-3. Radial longitudinal views of silica replicated tracheids 
from a laboratory silicified specimen of contemporary Sequoia sempervirens 
(redwood). Material was deorganicized prior to maceration. SEM. Magnifi- 
cations: Fig. | (X200), Fig. 2 (X500), and Fig. 3 (X1000). 
Figures 4-5. Comparable views from two deorganicized, naturally 
silicified, fossil Taxodiaceae. The discs are biconvex lenses which formed 
within the pit chamber. These lenses tend to break away from the cell wall 
surfaces during preparation of the specimen for microscopy. Figure 4: Fossil 
Wood (Sequoia sp.) of Miocene age from Virgin Valley, Nevada. SEM. 
X300. Figure 5: Fossil wood (Taxodiaceae) of Oligocene age from near 
Florissant, Colorado. SEM. X750. 
Figures 6-7. White light photomicrographs showing a vertical section 
through a multilayered algal mat from the Persian Gulf which was silicified 
with ethyl silicate. White area appearing in Figure 7 is a vein of silica 
produced during silicification. Both X260. 
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