Idioblasts may produce crystals

Needle-like crystals are raphides

Secretory structures may appear as single cells (secretory idioblasts) as in the case of oil cells, crystal containing cells, or tannin cells. In these cases, secretory product(s) are accumulated in the vacuole.

Crystals, most often calcium oxalate, may take the form of long needles (raphides) which lie in large parallel bundles in the stem parenchyma of corn plant (Dracena sp.). Such crystals show birefringence with polarized light as illustrated in the right-hand micrograph.