The Amaryllidaceae (amaryllids) are a family, the amaryllis family, of herbaceous, mainly perennial and bulbous (rarely rhizomatous) flowering plants included in the monocot order Asparagales. The family takes its name from the genus Amaryllis, hence its common name. The leaves are usually linear, and the flowers are usually bisexual and symmetrical, arranged in umbels on the stem. The petals and sepals are undifferentiated as tepals, which may be fused at the base into a floral tube. Some also display a corona. Allyl sulfide compounds produce the characteristic odour of the onion subfamily (Allioideae).