Bui. 606, U. S. Dept. of Agriculture. 
Plate IV. 
Post Oak, A White Oak (Radial Section, Magnified 50 Diameters). 
SP, springwood; SW, sumraerwood; MR, medullary ray; V, pores or vessels; X, wood pros- 
enchyrna (fibers, etc.);' T /tyloses. 
