Elaiosome

Elaiosomes (Ancient Greek: ἔλαιον élaion "oil" + σόμα sóma "body") are fleshy structures that are attached to the seeds of many plant species.

This type of seed dispersal is termed myrmecochory from the Greek "ant" (myrmex) and "circular dance" (khoreíā).

This type of symbiotic relationship appears to be mutualistic, more specifically dispersive mutualism according to Ricklefs, R.E.

[1] The various origins and developmental pathways apparently all serve the same main function, i.e. attracting ants.

A fully referenced current list of plants that have seeds with elaiosomes can be found in Lengyel et al.