are called by the general
name of _Panicles_. The heads of Compositae are centripetal; but the
branches or peduncles which bear the heads are usually of centrifugal
order.

Sec. 2. PARTS OR ORGANS OF THE FLOWER.

228. These were simply indicated in Section II. 16. Some parts are
necessary to seed-bearing; these are _Essential Organs_, namely, the
_Stamens_ and _Pistils_. Others serve for protection or for attraction,
often for both. Such are the leaves of the Flower, or the _Floral
Envelopes_.

229. =The Floral Envelopes=, taken together, are sometimes called the
PERIANTH, also _Perigone_, in Latin form _Perigonium_. In a flower which
possesses its full number of organs, the floral envelopes are of two
kinds, namely, an outer circle, the CALYX, and an inner, the COROLLA.

230. =The Calyx= is commonly a circle of green or greenish leaves, but
not always. It may be the most brightly colored part of the blossom.
Each calyx-leaf or piece is called a SEPAL.

231. =The Corolla= is the inner circle of floral envelopes or
flower-leaves, usually of delicate texture and _colored_, that is, of
some other color than green. Each corolla-leaf is called a PETAL.

232. There are flowers in abundance which consist wholly of floral
envelopes. Such are the so-called full _double flowers_, of which the
choicer roses and camellias of the cultivator are familiar examples. In
them, under the gardener's care and selection, petals have taken the
place of both stamens and pistils. These are monstrous or unnatural
flowers, incapable of producing seed, and subservient only to human
gratification. Their common name of _double_ flowers is not a sensible
one: except that it is fixed by custom, it were better to translate
their Latin name, _flores pleni_, and call them _full flowers_, meaning
full of leaves.

233. Moreover, certain plants regularly produce _neutral flowers_,
consisting of floral envelopes only. In Fig. 214, some are seen around
the margin of the cyme in Hydrangea. They are likewise familiar in the
Hobble-bush and in Wild-Cranberry tree, Viburnum Oxycoccus; where they
form an attractive setting to the cluster of small and comparatively
inconspicuous perfect flowers which they adorn. In the Guelder Rose, or
Snow-ball of ornamental cultivation, all or most of the blossoms of this
same shrub are transformed into neutral flowers.

[Illustration: Fig. 218. A _flos plenus_, namely, a full double flower
of Rose.]

234. =The Ess