An unusual arrangement of smooth membranes in the root meristem cells of Allium cepa L. following exposure to colchicine.

The unusual membranes in the root meristem cells of Allium cepa after exposure to colchicine are arranged in a closed multilayered structure consisting of a pair of double unit membranes enclosing a ground substance which consists essentially of ribosomes. The spaces between the unit membranes and between the pairs of unit membranes are uniform throughout the entire organelle. There is some indication of the association of this organelle with mitochondria.