The nature of precipitates formed in the outer cell wall following fixation of leaf tissue with Gilson solution.

The nature of precipitates formed in the outer cell walls of leaf tissue fixed in Gilson solution, used extensively to demonstrate ectodesmata, is described. Electron-microbe X-ray analysis established that the crystalline precipitates contained both mercury and chlorine. Based on solubility in water and ethanol, birefringence and ratio of mercury to chlorine, the chemical form is probably mercurous chloride. Further treatment of the leaf tissue with potassium iodide caused the crystalline precipitate to turn black and lose birefringence when viewed with plane-polarized light. Analysis of this precipitate showed the presence of only mercury, chlorine having been lost.