62 



ON THE TLANT-CELL. 



cover of a Chinese casket. At a cursory first glance the transverse sec- 

 tion (fig. 53.) appears to exhibit clearly defined annual rings. More ac- 

 curate research shows that the dark stripes which, as the most external 



part of an annual ring, appear, are not connected, but form isolated 

 transverse bands between the two medullary rays. These transverse 



51 Transverse section of the wood of Bombax pentandra. The entire wood consists ot 

 thin- walled but porous parenchyma (c), in which individual thick-walled wood-cells (t) 

 are scattered. Small medullary rays, consisting of individual rows of cells, pass through 

 the wood at pretty regular distances. In the under half of the section, the cell-walls 

 become imperceptibly thicker, by which the boundaries of the two annual rings are 

 clearly indicated. Single or in pairs, porous cells, lying on one another, pass through 

 the wood (c). 



58 Longitudinal section of the same wood. a, Porous vessels, b, Wood-cells. 

 c, Parenchyma. 



53 Transverse section of wood from a Chinese casket, with a low magnifying 

 power. At first sight, the dark transverse bands might be regarded as the boundaries 

 of the annual rings. They are not, however, connected together, and each extends 

 between the medullary rays. The small space marked at x is strongly magnified at 

 fig. 54., where it will be seen that the dark bands are formed out of small stripes of 

 wood-cells, which alternate with a thin-walled porous parenchyma (c). Between the 

 wood-cells and the medullary rays there exists also a layer of thin-walled parenchyma- 

 cells. Between the wood-cells may be observed radial rows of somewhat broader and 

 smaller thick-walled wood-cells. The thin-walled medullary ray cells (?) are also 

 porous. Fig. 55. is a longitudinal section, parallel to the medullary rays ; and the 

 letters a, b, c indicate the same parts as in fig. 54. Large porous vessels are seen in 

 fig. 53., which are not represented in the other figures. 



