The characters which separate this from the first Sub-class, the
Choripetalæ, have been described on page 336. They consist in the
following: the flower is always verticillate, generally with =5=
sepals, =5= petals, =5= stamens, and =2= carpels (in the median plane),
the calyx is generally persistent and gamosepalous, the corolla is
gamopetalous and united to the stamens, which are therefore adnate to
it, the ovules have only _one_ thick integument and a small nucellus.
(The exceptions are noted later.)
This Sub-class is no doubt more recent than the Choripetalæ; it
is also peculiar in including fewer trees and shrubby forms than
the latter.