A. Cross-section of calamus rhizome" (Acorus calamus, L.). I, Intercel- 

 lular space; 2, Parenchyma cells; 3, Secretion cavity. B. Cross-section of 

 white pine bark (Pinus strobus, L.). 1, Parenchyma; 2, Secretion cavity; 

 3, Secretion cells. 



