The presence of domatia or foveoles on the undersurface of the leaf (or leaflet in the case of compound leaves) as seen with the naked eye. Domatia are structures in the forks of the midrib and the main lateral veins. They take two main forms, either conspicuous little tufts of hairs or small hooded enclosures (foveoles, i.e. small pits). Domatia may also occur in the forks formed by the branching of the main lateral veins but this is not a frequent occurrence.