Polysaccharide elementary fibrils are usually fasciated into microfibrils of from one hundred to a few hundred Angstroms wide. Cellulose microfibrils when subjected to acid treatment dissociate into component elementary fibrils. For pectic acid it was observed that variations in pH could cause a change in the fasciation of the elementary fibrils.Solutions of purified pectic acid and sodium phosphotungtate were adjusted to various pH levels with NaOH or HCl and diluted to give a final concentration of 0.5 and 1% for the polysaccharide and negative stains respectively. Micrographs were made of the samples after drying on a carbon film covered grid. The average number of elementary fibrils was determined by counting the number of elementary fibrils in each fascicle intersected by lines drawn across the micrograph.