<p>The diaspores of <i>Lepidosperma</i> Labill. (Cyperaceae) have thickened perianth members persistent at the base of the fruit, which are generally assumed to form a unique type of elaiosome but this assumption has not been tested rigorously. We tested whether the perianth provides a lipid-rich food reward and improves diaspore removal by ants in three species of <i>Lepidosperma</i>. We measured (i) the lipid and fatty acid composition of the fruit and perianth of two species of <i>Lepidosperma</i>, and of the seed and aril of two species of <i>Acacia</i> (known myrmecochores), (ii) the relative attractiveness to ants of the perianth in three species of <i>Lepidosperma</i>, and (iii) the relative attractiveness to ants of the diaspores of the same species of <i>Lepidosperma</i> compared with the two species of <i>Acacia</i>. We found that (i) <i>Lepidosperma</i> diaspores show traits consistent with myrmecochory, particularly the high lipid content (~12-60%) and fatty acid profile of perianth material, (ii) isolated perianth members were removed in greater numbers over all times than were diaspores only (i.e. with perianth removed) in two species of <i>Lepidosperma</i> (<i>n</i> = 100, <i>P</i> = 0.035 and 0.047), whereas the difference was equivocal in the third species (<i>n</i> = 100, <i>P</i> > 0.05), and (iii) <i>Lepidosperma</i> and <i>Acacia</i> diaspores were removed in similar numbers over time (<i>n</i> = 100, <i>P</i> > 0.5). Seven species of diaspore-removing ant were observed, with <i>Rhytidoponera metallica</i> accounting for ~50% of observed removals. We conclude that the perianth members of <i>Lepidosperma</i> are an elaiosome that provides a lipid-rich food reward.</p>