CELL-CONTENTS AND FORMS OF CELLS. 201 



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in Cannabis sativa, do not usually have a stalk, and are known 

 as " hair cystoliths." The latter are, furthermore, variously modi- 

 fied, and may have incrustations of either calcium carbonate or 

 silica or a mixture of both of these substances. In the Begoniacese 

 occurs a certain form of structure resembling a cystolith, but it is 

 uncalcified, and consists of a mucilaginous substance which is 



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3F^W 



FIG. 113. Cystolith. A cross section of a portion of the leaf of Ficus elastica showing 

 cells of the upper epidermis (e), cells of the hypodermal layer (h), among which is a large 

 cell containing a cystolith (c); palisade cells (ch). After Sachs. 



sometimes more or less impregnated with resin. These are known 

 as ' cystotyles." The protuberances found on the walls of 

 certain epidermal cells and in the subsidiary cells of hairs may 

 be either calcified or silicified, and occur in the families containing 

 true cystoliths and also some genera of the following: Com- 

 positae, Campanulacese, Oleaceae, Leguminosse, Hydrophyllaceas, 



