Fine structure of a crystal-containing plastid in Colchicum autumnale.

A study has been made of plastids in the root meristem of Colchicum autumnale. These organelles contain simultaneously deposits of starch, lipid, and a crystalline material, probably protein. Two types of internal membrane are present within the plastid. One appears to be concerned with the transport of material across the plastid envelope. The other has a special relationship to the crystal. The crystal is seen as long columns when cut in longitudinal section, and the membrane there is dark staining material, which is sometimes seen in the form of a large more or less rectangular body. The possible significance of these internal structures is discussed in relation to recent ideas on the development and functions of plastids in general.