Fig. 10.5-2. Transverse section of leaf of hemp (also marijuana; Cannabis sativa). The epidermis of this hemp leaf has numerous lithocysts that protrude out from the leaf, rather than into the leaf like the lithocysts of Ficus.

            In the high magnification view, the wall ingrowth is visible. Calcium carbonate does not begin crystallizing in the cytoplasm or vacuole, but only at the surface of this wall ingrowth. In the lower lithocyst, the calcium carbonate has grown into a large cystolith that it occupies most of the cell. Notice that the section is very thick (the mesophyll of the leaf has many out-of-focus cells in the background); because lithocysts are so large and the wall ingrowth is so small, there is a higher probability of catching an ingrowth in a thick section compared to a thin section.