ontains a thickish protoplasmic fluid, often
rendered turbid by an immense number of minute particles that float in
it. As the pollen matures this fluid usually dries up, but the
protoplasm does not lose its vitality. When the grain is wetted it
absorbs water, swells up, and is apt to burst, discharging the contents.
But when weak syrup is used it absorbs this slowly, and the tough inner
coat will sometimes break through the outer and begin a kind of growth,
like that which takes place when the pollen is placed upon the stigma.

[Illustration: Fig. 314. Magnified pollen of Hibiscus and other
Mallow-plants, beset with prickly projections; 315, of Circaea, with
angles bearing little lobes; 316, of Evening Primrose, the three lobes
as large as the central body; 317, of Kalmia, four grains united, as in
most of the Heath family; 318, of Pine, as it were of three grains or
cells united; the lateral empty and light.]

298. Some pollen-grains are, as it were, lobed (as in Fig. 315, 316), or
formed of four grains united (as in the Heath family, Fig. 317): that of
Pine (Fig. 318) has a large rounded and empty bladder-like expansion
upon each side. This renders such pollen very buoyant, and capable of
being transported to a great distance by the wind.

299. In species of Acacia simple grains lightly cohere into globular
pellets. In Milkweeds and in most Orchids all the pollen of an
anther-cell is compacted or coherent into one mass, called a
_Pollen-mass_, or POLLINIUM, plural POLLINIA. (Fig. 319-322.)

[Illustration: Fig. 319. Pollen, a pair of pollinia of a Milkweed,
Asclepias, attached by stalks to a gland; moderately magnified.]

[Illustration: Fig. 320. Pollinium of an Orchis (Habenaria), with its
stalk attached to a sticky gland; magnified. 321. Some of the packets or
partial pollinia, of which Fig. 320 is made up, more magnified.]

[Illustration: Fig. 322. One of the partial pollinia, torn up at top to
show the grains (which are each composed of four), and highly
magnified.]

Section X. PISTILS IN PARTICULAR.

Sec. 1. ANGIOSPERMOUS OR ORDINARY GYNOECIUM.

300. =Gynoecium= is the technical name for the pistil or pistils of a
flower taken collectively, or for whatever stands in place of these. The
various modifications of the gynoecium and the terms which relate to
them require particular attention.

301. The PISTIL, when only one, occupies the centre of the flower; when
there are two pistils, they stand f