Wood from the buried Forest. 



77 



communication of fiber with fiber. No such membrane could 

 be detected in the buried forest specimens. 



The medullary rays (m r) are very minute, narrow and quite 

 uniformly distributed sheets of parenchymatous tissue. There 

 are about 40 rays to the square millimeter of surface (in tan- 

 gential section). The rays are uniseriate — that is, one cell broad, 

 as in most coniferse. The breadth of the ray is thus measured 

 by that of the medullary cell, which is about -g-^ mm. The height 

 of the rays varies from about 2V ^^ f mm, and is from three to 

 about seventeen cells deep. The medullary rays exactly fill the 

 meshes between the bundles of wood-fibers. In some cases the 

 cell-walls of the parenchyma have undergone alteration, and 

 contain the brownish deposit (d) already noticed. 



The transverse section shows parts of two annual rings or layers 

 (figure 5). In one (the later growth — late summer or autumn, 



FiGiTRE 5 — Transverse Section of Wood from the buried Forest. 



a g = Outer portion of annual layer representing later growth ; vg,= 

 Inner portion of succeeding annular layer, representing earlier growth ; 

 d = Deposit in cell of medullary ray ; mr^ Medullary ray ; ac = Altered 

 cell wall of parenchymatous tissue ; p = Pit-cavity ; x = Internal opening 

 of pit ; t = Tracheide. 



a, g) the cells are flattened and have very thick walls ; in the 

 other (the earlier growth — spring or early summer, v, g) the cells 

 are much larger, and the walls are thinner. Pits occur in both 



