SCIENTIFIC AND APPLIED PHARMACOGNOSY 



FIG. 17. Cross-section of bark of Tsuga canadensis. c, c, c, secondary cork 

 formation; a, dead phloem tissues rich in coloring, resinous and tannin-like 

 substances; s, s, stone cells; m, m, medullary rays; cr, cells containing 

 long prisms of calcium oxalate; ca, cambium; st, bands of starch-bearing 

 parenchyma cells. B, tangential-longitudinal section of inner bark showing 

 medullary ray cells (a) and crystal cells (c); an oleoresin-secretion cell (s). 

 C, stone cells from the inner bark (b). D, various forms of prismatic crystals 

 of calcium oxalate. After Bastin. 



