THE CELL 17 
certain stains. The cytoplasm of many, possibly of all, 
plant cells contains, scattered through it, numerous tiny, 
deeply staining granules, called chondriosomes. 
(a) The cytoplasm appears net-like, or reticular, in 
structure, and the spaces between the meshes are vacuoles. 
Each vacuole is filled with an aqueous solution of various 
FIG. 9. Diagram of a plant cell in perspective, with portions of adja- 
cent cells. Note the nucleus. The lighter areas are vacuoles in the 
cytoplasm. 
substances, known as the cell-sap. Insoluble solids of 
various nature, such as crystals and starch grains, com- 
monly occur in the vacuoles. 
(b) At every free surface, such as the outer surface and 
the walls of the vacuoles, the cytoplasm is specially organ- 
ized into a limiting membrane (or plasma-membrane). 
The structure of this membrane is not well understood, 
