Term:

Pulvinulus (pl. = pulvinulus, adj. = pulvinate or pulvinulate)
Definition:

An enlargement at the base of the petiole or petiolule of leaves.
Notes:

Pulvinuli can be found at the base or the apex or at both the base and apex of petioles or petiolules. The can also be referred to to describe swollen areas at the base of other structures, e.g., the bases of rachises of inflorescences. Pulivini are found in many plant families but they are especially frequent in members of the legume family (Fabaceae).
Related Terms:

Petiole
Petiolule