Well-defined polypetalous and gamopetalous genera sometimes occur in the same order, and even Monocotyledons and Dicotyledons are classed together where they have some .striking physiological character in common.
The general name of polypetalous is given to corollas having separate petals, while monopetalous, gamopetalous or sympetalous is applied to those in which the petals are united.
TROPICAL REGI0N.This is characterized by the presence of gigantic Monocotyledons, palms, Musaceae and bamboos, and of evergreen polypetalous trees and figs.
The sequence of orders in the polypetalous subdivision of Dicotyledons undoubtedly represents a progression from simpler to more elaborate forms, but a great drawback to the value of the system is the inclusion among the Monochlamydeae of a number of orders which are closely allied with orders of Polypetalae though differing in absence of a corolla.
Amongst regular polypetalous corollas may be noticed the rosaceous corolla (fig.