A Survey of Oil Cells in the Dicotyledons With Comments on Their Replacement by and Joint Occurrence With Mucilage Cells

Anatomy, ultrastructure and development of mucilage and oil cells in the dicotyledons are reviewed, and a bibliography of the records for oil cells is given. In several families normally characterized by oil cells some of the species also have mucilage cells, or the oil cells seem to be “replaced” by mucilage cells. In other taxa intermediates between oil and mucilage cells have been reported in the literature. This poses the question of a possible homology of oil and mucilage cells, despite their very different attributes in the fully mature state. The taxonomic and phylogenetic significance of oil and mucilage cells is briefly discussed. The need for a comparative developmental, ultrastructural and biochemical study of critical taxa is stressed.