PLANT ORGANS AND ORGANISMS 
III 
Wood.- — From a pharmacognic standpoint as well as that of the 
lumber trade, wood is all that portion of woody exogenous plant 
axes inside of the cambium line. In Dicotyl and Gymnosperm 
stems it therefore includes the xylem regions of the bundles, the 
st 
Fig. 49. — Photomicrograph of transverse section of Cascara Sagrada bark; 
k, cork; g, cork cambium; c, cortex; st, group of stone cells; bf, group of bast fibers; 
mr, medullary ray. 
xylem portions of the medullary rays and the pith, while in the roots 
of secondary growth of these plants it comprises the xylem portions 
of the bundles and the xylem medullary rays. 
As the cambium year after year adds new layers of wood to that 
