▁called ▁a ▁" p ale a " ▁or ▁" re cept ac ular ▁b ract ". ▁These ▁b ract s ▁are ▁often ▁called ▁" ch aff ". ▁The ▁presence ▁or ▁absence ▁of ▁these ▁b ract s , ▁their ▁distribution ▁on ▁the ▁re cept acle , ▁and ▁their ▁size ▁and ▁shape ▁are ▁all ▁important ▁di agnostic ▁characteristics ▁for ▁gener a ▁and ▁tribes . ▁ ▁The ▁flor ets ▁have ▁five ▁pet als ▁f used ▁at ▁the ▁base ▁to ▁form ▁a ▁cor ol la ▁t ube ▁and ▁they ▁may ▁be ▁either ▁act in omorphic ▁or ▁z yg omorphic . ▁Disc ▁flor ets ▁are ▁usually ▁act in omorphic , ▁with ▁five ▁pet al ▁lips ▁on ▁the ▁rim ▁of ▁the ▁cor ol la ▁t ube . ▁The ▁pet al ▁lips ▁may ▁be ▁either ▁very ▁short , ▁or ▁long , ▁in ▁which ▁case ▁they ▁form ▁deeply ▁lo bed ▁pet als . ▁The ▁latter ▁is ▁the ▁only ▁kind ▁of ▁fl oret ▁in ▁the ▁Card uo ide ae , ▁while ▁the ▁first ▁kind ▁is ▁more ▁w ides p read . ▁Ray ▁flor ets ▁are ▁always ▁highly ▁z yg omorphic ▁and ▁are ▁character ised ▁by ▁the ▁presence ▁of ▁a ▁lig ule , ▁a ▁st rap - sh aped ▁structure ▁on ▁the ▁edge ▁of ▁the ▁cor ol la ▁t ube ▁consisting ▁of ▁f used ▁pet als . ▁In ▁the ▁Ast ero ide ae ▁and ▁other ▁minor ▁sub famil ies ▁these ▁are ▁usually ▁bor ne ▁only ▁on ▁flor ets ▁at ▁the ▁circum ference ▁of ▁the ▁capit ul um ▁and ▁have ▁a ▁ 3 +