ential Organs= are likewise of two kinds, placed one above
or within the other; namely, first, the STAMENS or fertilizing organs,
and second, the PISTILS, which are to be fertilized and bear the seeds.

[Illustration: Fig. 219. A stamen: _a_, filament; _b_, anther,
discharging pollen.]

[Illustration: Fig. 220. A pistil; with ovary, _a_, half cut away, to
show the contained ovules; _b_, style; _c_, stigma.]

235. =A Stamen= consists of two parts, namely, the FILAMENT or stalk
(Fig. 219 _a_), and the ANTHER (_b_). The latter is the only essential
part. It is a case, commonly with two lobes or cells, each opening
lengthwise by a slit, at the proper time, and discharging a powder or
dust-like substance, usually of a yellow color. This powder is the
POLLEN, or fertilizing matter, to produce which is the office of the
stamen.

236. =A Pistil= (Fig. 220, 221) when complete, has three parts; OVARY,
STYLE, and STIGMA. The _Ovary_, at base, is the hollow portion, which
contains one or more OVULES or rudimentary seeds. The _Style_ is the
tapering portion above: the _Stigma_ is a portion of the style, usually
its tip, with moist naked surface, upon which grains of pollen may lodge
and adhere, and thence make a growth which extends down to the ovules.
When there is no style then the stigma occupies the tip of the ovary.

[Illustration: Fig. 221. Model of a simple pistil, with ovary cut across
and slightly opened ventrally, to show the ovules and their attachment.]

237. =The Torus= or =Receptacle= is the end of the flower-stalk, or the
portion of axis or stem out of which the several organs of the flower
grow, upon which they are borne (Fig. 223).

[Illustration: Fig. 222. Flower of Sedum ternatum, a Stonecrop.]

[Illustration: Fig. 223. Parts of same, two of each kind, separated and
displayed; the torus or receptacle in the centre; _a_, a sepal; _b_, a
petal; _c_, a stamen; _d_, a pistil.]

238. The parts of the flower are thus disposed on the receptacle or axis
essentially as are leaves upon a very short stem; first the sepals, or
outer floral leaves; then the petals or inner floral leaves; then the
stamens; lastly, at summit or centre, the pistils, when there are two or
more of them, or the single pistil, when only one. Fig. 223 shows the
organs displayed, two of each kind, of such a simple and symmetrical
flower as that of a Sedum or Stonecrop, Fig. 222.

Sec. 3. PLAN OF FLOWER.

239. All flowers are formed upon o