The morphology and distribution patterns of oil and mucilage cells in the leaf of 150 species of Cinnamomum are described. Idioblasts are always present in the palisade and the spongy parenchyma. Usually both oil and mucilage cells occur; in some species either oil or mucilage cells are present. Both types of idioblasts possess a suberized wall layer. The idioblasts vary between species in size/ shape, stainability and number. Variations in the distribution pattern can partly be explained by the proposed homology of the oil and mucilage cells. Other leaf anatomical characters are also mentioned, such as lamina and cuticle thickness, bundle sheath extensions, sclerification of the epidermal, the palisade, and the spongy parenchyma cells, number of palisade layers, presence or absence of a hypodermis, the indumentum and papillate abaxial epidermal cells, and the venation pattern. Most species differ from each other in only one or few leaf anatomical characters (including oil and mucilage cells). A great many combinations in character distribution were observed. However, the distribution pattern in approximately one-fifth of all studied species deviated largely from the typical leaf anatomical character distribution pattern occurring in the majority of Cinnamomum species. There was a maximum of seven differing features out of the sixteen features studied. Within this group almost all neotropical Cinnamomum species are included. The latter species lack sclerified epidermal cells and almost all have penninerved instead of the generally occurring triplinerved leaves. Cluster analyses based on all leaf anatomical features studied revealed that the distribution patterns of the oil and mucilage cells play a significant part in the grouping of the species. Therefore oil and mucilage cells possess at least some diagnostic value within the genus Cinnamomum. The systematic significance of oil and mucilage cells at the infrageneric level remains uncertain for lack of a detailed infrageneric classification of Cinnamomum for comparison with the idioblast distribution patterns.

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Journal Blumea: Biodiversity, Evolution and Biogeography of Plants

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Bakker, M.E, Gerritsen, A.F, & van der Schaaf, P.J. (1992). Leaf anatomy of Cinnamomum schaeffer (Lauraceae) with special reference to oil and mucilage cells. Blumea: Biodiversity, Evolution and Biogeography of Plants, 37(1), 1–30.