Abstract: Comparative observations were made on the morphology and anatomy of secretory cavities in leaves of 22 genera, 40 species and two varieties by the whole mounting, paraffin and thin section method. A mature cavity consists of one layer of epithelial cells surrounding a large intercellular space and one to five layers of peripheral sheath cells. The epithelial cells were flattened, thin-walled and integrated, which suggests that the cavities developed schizogenously. The sheath cells were also flattened. The cell walls of the outer layers had relative thickenings. The number of layers of the sheath cells varied with species. A few of species appeared to lack the sheath cells. The localization and structure of the cavities were correlated with taxa at generic and specific level. According to their structural features and arrangement in leaves, the secretory cavities can be grouped into four types as follows: the notch type (between the leaf-teeth), the mesophyll type which is subdivided into spongy parenchyma subtype and palisade parenchyma subtype, and the mixed type (with both notch and mesophyll cavities). Based on these observations evolutionary trends concerning the morphology and anatomy of cavities and affinity among subfamilies or genera are discussed. It issuggested that the mixed type of cavities developed from the notch and mesophyll types.

Key words: Rutaceae, Secretory cavities, Comparative anatomy