Mesophyll cell walls in hemlock, Tsuga canadensis

Observations have been made on the walls of the mesophyll cells in the leaves of hemlock, Tsuga canadensis, to determine if there were any structural features which would account for the relatively high resistance measured at the mesophyll cell surface in infiltrated leaves by Tyree et al. (1975). There was no indication of an internal cuticle based on histochemical tests of fresh sections and the appearance of the wall in electron micrographs. Examination of Alcian-blue-stained fresh sections and thin sections of material treated with ruthenium red indicated that mesophyl) cell walls may be covered with a mucilaginous layer that retards the evaporation of water to intercellular spaces.