Hypanthium

In angiosperms, a hypanthium or floral cup is a structure where basal portions of the calyx, the corolla, and the stamens form a cup-shaped tube. It is sometimes called a floral tube, a term that is also used for corolla tube and calyx tube. It can often contain the nectaries of the plant. It is present in most flowering species, although varies in structural dimensions and appearance. This differentiation between the hypanthium in particular species is useful with identification. Some geometric forms are obconic shapes as in toyon, whereas some are saucer-shaped as in Mitella caulescens.