A Mucilaginous Root Sheath in Ericaceae

A prominent mucilaginous sheath surrounding the root tips of plants in the family Ericaceae is described. The sheath was ubiquitous in all species examined. These included representatives of both subfamilies and all tribes of the family. Anatomical studies indicated that the sheath was not the breakdown product of root cap cells but rather that it was formed exterior to a thickened cell wall or cellular layer at the root tip. Although the mucilaginous sheath stained readily with ruthenium red (a specific test for pectins), it was not possible to show it to be one of the common pectins by microchemical tests. Relationships between the soil environment and the extent and condition of the sheath are discussed. Possible significance or functions of the sheath are suggested.