llustration: Fig. 260. A small Passion-flower, with crown of slender
threads.]

262. Such petals, and various others, may have an outgrowth of the inner
face into an appendage or fringe, as in Soapwort, and in Silene (Fig.
259), where it is at the junction of claw and blade. This is called a
CROWN, or _Corona_. In Passion-flowers (Fig. 260) the crown consists of
numerous threads on the base of each petal.

[Illustration: Fig. 261. Front view of a papilionaceous corolla. 262.
The parts of the same, displayed: _s_, Standard, or Vexillum; _w_,
Wings, or Alae; _k_, Keel, or Carina.]

263. =Irregular Flowers= may be polypetalous, or nearly so, as in the
papilionaceous corolla; but most of them are irregular through
coalescence, which often much disguises the numerical symmetry also. As
affecting the corolla the following forms have received particular
names:

264. =Papilionaceous Corolla=, Fig. 261, 262. This is polypetalous,
except that two of the petals cohere, usually but slightly. It belongs
only to the Leguminous or Pulse family. The name means butterfly-like;
but the likeness is hardly obvious. The names of the five petals of the
_papilionaceous_ corolla are curiously incongruous. They are,

The STANDARD or _Banner_ (_Vexillum_), the large upper petal which is
external in the bud and wrapped around the others.

The WINGS (_Alae_), the pair of side petals, of quite different shape
from the standard.

The KEEL (_Carina_), the two lower and usually smallest petals; these
are lightly coalescent into a body which bears some likeness, not to the
keel, but to the prow of a boat; and this encloses the stamens and
pistil. A Pea-blossom is a typical example; the present illustration is
from a species of Locust, Robinia hispida.

265. =Labiate Corolla= (Fig. 256-258), which would more properly have
been called _Bilabiate_, that is, two-lipped. This is a common form of
gamopetalous corolla; and the calyx is often bilabiate also. These
flowers are all on the plan of five; and the irregularity in the corolla
is owing to unequal union of the petals as well as to diversity of form.
The two petals of the upper or posterior side of the flower unite with
each other higher up than with the lateral petals (in Fig. 256, quite to
the top), forming the _Upper lip_: the lateral and the lower similarly
unite to form the _Lower lip_. The single notch which is generally found
at the summit of the upper lip, and the two notches of the low