Calcium oxalate crystals in the stem of Sida hermaphrodita (L.) Rusby (Malvaceae)

Observations of calcium oxalate crystals of the stem of an energetic plant S. hermaphrodita (L.) Rusby from the Malvaceae family, were performed using LM, DIC, and CLSM microscopes. The transversal and longitudinal sections showed the presence of calcium oxalate crystals in the parenchymal tissue distributed in various layers of the stem. The crystals occurred only in the form of druses. In the innermost part of the stem, i.e. in the pith, the calcium oxalate crystals occurred singly in individual cells. In the parenchyma cells separating sclerenchyma fibres and adjacent to the xylem, the crystals were observed individually in single cells, but the cells containing druses formed rows consisting of even several cells. The cortex contained the different-size druses scattered randomly within the cells. Druses differ in shape and size but they do not protrude beyond the cells although they very often fill them completely. The functions of calcium oxalate crystals are discussed