CELL CONTENTS 215 



Cystoliths occur, then, in special cavities, in parenchyma 

 cells (rubber-plant leaf, fig, pellionea, and mulberry), and in 

 non-glandular hairs (cannabis indica). 



In powdered ruellia root the cystoliths occur in or are sepa- 

 rated from the parenchyma cells. 



TESTS FOR CYSTOLITHS 



When dilute hydrochloric acid or acetic acid is added to 

 cystoliths a brisk effervescence takes place with the evolution 

 of carbon dioxide gas. 



