CHAPTER I. — THE CELL. 



M3 



Mineral Substances. The cell-sap contains many inor- 

 ganic substances in solution, such as oxygen, nitrogen, carbon 

 dioxide, silica, and salts of potassium, sodium, calcium, mag- 

 nesium and iron. Silica and salts of calcium, as has already 

 been stated, are often deposited, either in the amorphous or 

 crystalline form, in the substance of the cell-wall. But, besides 

 these, crystals of mineral matter are often found in the interior 

 of cells. 



The most common of these are calcium oxalate and calcium 

 carbonate, but calcium phosphate, calcium sulphate and silica 



Fig 388. 



Fig. 387.— Mass of sphere-crystals from the underground stem of Aralia nudicaulis. 

 Magnified about 375 diameters. 



Fig. 388.' -Cell containing a bundle of raphides from the rhizome of Trillium grandi- 

 florum. Magnified about 250 diameters. 



Fig. 389. — Portion of cross-section of leaf of Ficus elastica, showing large cell con- 

 taining a cyatolith. Magnified about 250 diameters. 



are sometimes, though rarely, found among the cell contents. 

 Crystals of calcium oxalate are by far the most common, and 

 they are found in a great variety of forms. 



They may occur singly or in clusters. Figures 384 and 385 

 represent some single forms from the petiole of Begonia and the 

 leaf of Agave, respectively ; Fig. 386, another form from the leaf 

 of Agave; Fig. 387, a mass of sphere-crystals from the under- 

 ground stem of Aralia nudicaulis, and Fig. 388 represents a bundle 

 of raphides, or needle-like crystals, of the same substance, from 



