EXPLANATION OF THE ILLUSTRATION 
Plate 2. Scanning electron micrograph (SEM) of silica replicated structures 
from three petrified woods of the Taxodiaceae, emphasizing tracheid end 
walls. All three specimens were deorganicized with concentrated nitric acid 
and potassium chlorate prior to maceration. 
Fig. 1 Radial longitudinal view of a contemporary wood, Sequoia sempervi- 
rens (redwood), silicified with ethyl silicate and then deorganicized. SEM. 
X200. 
Fig. 2. Radial longitudinal view of a naturally silicified wood of Upper 
Oligocene age from near Florissant, Colorado. SEM. X200. 
Fig.3. Enlargement of a portion of the surface of the specimen illustrated in 
Figure 1. SEM. X500. 
Fig. 4. Tracheid tip from a fossil Sequoia of Niocene age from near Emig- 
rant Gap, Sierra Nevada Mountains, California. SEM. X1000. 
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