WOOD-PARENCHYMA. 219 
The very dense wood of Lignum Quassia (Fig. 137) contains 
groups of parenchyma (p), which run transversly in the form of 
bands from one medullary ray to the other, and intersect the 
nM 
Fie. 136. Fic. 137. ‘ 
Fig, 136.—Schematic representation of a longitudinal section of two tracheids from 
coniferous wood, with the different forms of pitting of the membrane (a-d), viewed 
( . 
cWas tae iris Gaee aaune tele Quassice jamaicense; the medullary 
rays, which form two or three rows of cells (r), are connected by transverse bands of 
wood-parenchyma (p); between them is the libriform tissue. 
wood in the form of numerous, closely arranged concentric 
rings.’ By their wider and not thickened cells they present a — 
‘Compare also Berg’s “ Atlas,” plate xxvii., Fig. 65 (Lignum Cam- 
pechianum), plate xxvii., Fig. 64 (Lign. Guaiaci). oe 
. 
