Domatia. Domatium in Latin means “small house.” Domatia (pl.) are parts of plants that have been modified evolutionarily into cavities, serving as homes for other organisms, such as ants, mites, and even bacteria. The part of the plant that is modified can be a leaf, stem, or root, depending on the species. They may be simple structures, such as grooves at the base of leaves (e.g., on ash trees), or cavities formed by the over-arching of tissues where two leaf veins meet (coffee plant); or they may involve hollow stems (cecropias) or stipules (ant-acacias). In the genus Myrmecodia, the entire swollen root tubers are chambered and provide residences for ants. In still other plants swollen leaf nodules (as in Ardisia) house colonies of bacteria.

The pictures below of the upper (adaxial) and lower (abaxial) surfaces of the leaves of a coffee plant show domatia.