The distribution density of oil cells, the morphology and structure of both oil and
mucilage cells, and their localization in the mesophyll of 112 species, 5 varieties and 2 forms
in 21 genera of the Lauraceae are comparatively studied with the methods of tissue clearing
and paraffin sectioning. The results show that there exist obvious differences of the distribu-
tion density of oil cells among the species in the Lauraceae. The presence of oil cells and mu-
cilage cells is found to be a marked anatomical feature of the leaves in most of the plants in
the Lauraceae. Their distribution in the mesophyll can be divided into 4 types: type Ⅰ , in
which only oil cells are present; type Ⅱ, in which both the oil and mucilage cells are pre-
sent; type Ⅲ, in which only mucilage cells are present; type Ⅳ, in which neither oil cells
nor mucilage cells are present. The distribution density of oil cells, the distribution types of
oil cells and mucilage cells and their localization in the mesophyll are of some taxonomic value
at the specific level in the Lauraceae. In the whole Lauraceae or in some large genera, the
evolutionary trend of the distribution types of oil cells and mucilage cells might be as follows:
type Ⅰ → type Ⅱ →type Ⅲ →type Ⅳ. The characteristics of the 4 distribution types of oil
cells and mucilage cells support the division of two subfamilies in the Lauraceae.
