The seven series of Monocotyledons represent a sequence beginning with the most complicated epigynous orders, such as Orchideae and Scitamineae, and passing through the petaloid hypogynous orders (series Coronarieae) of which Liliaceae is the representative to Juncaceae and the palms (series Calycinae) where the perianth Ioses its petaloid character and thence to the Aroids, screw-pines and albuminous Dicotyledons the cotyledons act as the absorbents of the reserve-food of the seed and are commonly brought above ground (epigeal), either withdrawn from the seed-coat or carrying it upon them, and then they serve as the first green organs of the plant.
The petaloid perianth consists of two series, each with three members, which are joined below into a longer or shorter tube, followed by one whorl of three stamens; the inferior ovary is three-celled and contains numerous ovules on an axile placenta; the style is branched and the branches are often petaloid.
When the parts of the calyx are in appearance like petals they are said to be petaloid, as in Liliaceae.
They are usually of a greenish colour (herbaceous); but sometimes they are coloured or petaloid, as in the fuchsia, tropaeolum, globe-flower and pomegranate.
Sometimes, as in Canna, one of the anther-lobes becomes abortive, and a petaloid appendage is produced.