281. =Androecium= is a technical name for the staminate system of a
flower (that is, for the stamens taken together), which it is sometimes
convenient to use. The preceding section has dealt with modifications of
the flower pertaining mainly to calyx and corolla. Those relating to the
stamens are now to be indicated. First as to
282. Insertion, or place of attachment. The stamens usually go with the
petals. Not rarely they are at base
_Epipetalous_, that is, inserted on (or adnate to) the corolla, as in
Fig. 283. When free from the corolla, they may be
[Illustration: Fig. 283. Corolla of Morning Glory laid open, to show the
five stamens inserted on it, near the base.]
_Hypogynous_, inserted on the receptacle under the pistil or gynoecium.
_Perigynous_, inserted on the calyx, that is, with the lower part of
filament adnate to the calyx-tube.
_Epigynous_, borne apparently on the top of the ovary; all which is
explained in Fig. 270-274.
[Illustration: Fig. 284. Style of a Lady's Slipper (Cypripedium), and
stamens united with it; _a_, _a_, the anthers of the two good stamens;
_st_, an abortive stamen, what should be its anther changed into a
petal-like body; _stig_, the stigma.]
_Gynandrous_ is another term relating to insertion of rarer occurrence,
that is, where the stamens are inserted on (in other words, adnate to)
the style, as in Lady's Slipper (Fig. 284), and in the Orchis family
generally.
283. =In Relation to each Other=, stamens are more commonly
_Distinct_, that is, without any union with each other. But when united,
the following technical terms of long use indicate their modes of mutual
connection:--
_Monadelphous_ (from two Greek words, meaning "in one brotherhood"),
when united by their filaments into one set, usually into a ring or cup
below, or into a tube, as in the Mallow Family (Fig. 286), the
Passion-flower (Fig. 260), the Lupine (Fig. 287), and in Lobelia (Fig.
285).
[Illustration: Fig. 285. Flower of Lobelia cardinalis, Cardinal flower;
corolla making approach to the ligulate form; filaments (_st_)
monadelphous, and anthers (_a_) syngenesious.]
[Illustration: Fig. 286. Flower of a Mallow, with calyx and corolla cut
away; showing monadelphous stamens.]
[Illustration: Fig. 287. Monadelphous stamens of Lupine. 288.
Diadelphous stamens (9 and 1) of a Pea-blossom.]
_Diadelphous_ (meaning in two brotherhoods), when united by the
filaments into two sets, as in the Pea and most of its near relatives
(Fig. 288), usually nine in one set, and one in the other.
_Triadelphous_ (three brotherhoods), when the filaments are united in
three sets or clusters, as in most species of Hypericum.
_Pentadelphous_ (five brotherhoods), when in five sets, as in some
species of Hypericum and in American Linden (Fig. 277, 289).
_Polyadelphous_ (many or several brotherhoods) is the term generally
employed when these sets are several, or even more than two, and the
particular number is left unspecified. These terms all relate to the
filaments.
_Syngenesious_ is the term to denote that stamens have their anthers
united, coalescent into a ring or tube; as in Lobelia (Fig. 285), in
Violets, and in all of the great family of Compositae.
284. =Their Number= in a flower is commonly expressed directly, but
sometimes adjectively, by a series of terms which were the name of
classes in the Linnaean artificial system, of which the following names,
as also the preceding, are a survival:--
_Monandrous_, i. e. solitary-stamened, when the flower has only one
stamen,
_Diandrous_, when it has two stamens only,
_Triandrous_, when it has three stamens,
_Tetrandrous_, when it has four stamens,
_Pentandrous_, when it has five stamens,
_Hexandrous_, when with six stamens, and so on to
_Polyandrous_, when it has many stamens, or more than a dozen.
[Illustration: Fig. 289. One of the five stamen-clusters of the flower
of American Linden, with accompanying scale. The five clusters are shown
in section in the diagram of this flower, Fig. 277.]
[Illustration: Fig. 290. Five syngenesious stamens of a Coreopsis. 291.
Same, with tube laid open and displayed.]
285. For which terms, see the Glossary. They are all Greek numerals
prefixed to _-andria_ (from the Greek), which Linnaeus used for
_androecium_, and are made into an English adjective, _-androus_. Two
other terms, of same origin, designate particular cases of number (four
or six) in connection with unequal length. Namely, the stamens are
_Didynamous_, when, being only four, they form two pairs, one pair
longer than the other, as in the Trumpet Creeper, in Gerardia (Fig.
263), etc.
_Tetradynamous_, when, being only six, four of them surpass the other
two, as in the Mustard-flower and all the Cruciferous family, Fig. 235.
286. =The Filament= is a kind of stalk to the anther, commonly slender
or thread-like: it is to the anther nearly what the petiole is to the
blade of a leaf. Therefore it is not an essential part. As a leaf may be
without a stalk, so the anther may be _Sessile_, or without a filament.
[Illustration: Fig. 292. Stamen of Isopyrum, with innate anther. 293. Of
Tulip-tree, with adnate (and extrorse) anther. 294. Of Evening Primrose,
with versatile anther.]
287. =The Anther= is the essential part of the stamen. It is a sort of
case, filled with a fine powder, _the Pollen_, which serves to fertilize
the pistil, so that it may perfect seeds. The anther is said to be
_Innate_ (as in Fig. 292), when it is attached by its base to the very
apex of the filament, turning neither inward nor outward;
_Adnate_ (as in Fig. 293), when attached as it were by one face, usually
for its whole length, to the side of a continuation of the filament; and
_Versatile_ (as in Fig. 294), when fixed by or near its middle only to
the very point of the filament, so as to swing loosely, as in the Lily,
in Grasses, etc. Versatile or adnate anthers are
_Introrse_, or _Incumbent_, when facing inward, that is, toward the
centre of the flower, as in Magnolia, Water-Lily, etc.
_Extrorse_, when facing outwardly, as in the Tulip-tree.
288. Rarely does a stamen bear any resemblance to a leaf, or even to a
petal or flower-leaf. Nevertheless, the botanist's idea of a stamen is
that it answers to a leaf developed in a peculiar form and for a special
purpose. In the filament he sees the stalk of the leaf; in the anther,
the blade. The blade of a leaf consists of two similar sides; so the
anther consists of two LOBES or CELLS, one answering to the left, the
other to the right, side of the blade. The two lobes are often connected
by a prolongation of the filament, which answers to the midrib of a
leaf; this is called the CONNECTIVE. This is conspicuous in Fig. 292,
where the connective is so broad that it separates the two cells of the
anther to some distance.
[Illustration: Fig. 295. Diagram of the lower part of an anther, cut
across above, and the upper part of a leaf, to show how the one answers
to the other; the filament to petiole, the connective to midrib; the two
cells to the right and left halves of the blade.]
289. A simple conception of the morphological relation of an anther to a
leaf is given in Fig. 295, an ideal figure, the lower part representing
a stamen with the top of its anther cut away; the upper, the
corresponding upper part of a leaf.
290. So anthers are generally _two-celled_. But as the pollen begins to
form in two parts of each cell (the anterior and the posterior),
sometimes these two strata are not confluent, and the anther even at
maturity may be _four-celled_, as in Moonseed (Fig. 296); or rather, in
that case (the word _cell_ being used for each lateral half of the
organ), it is _two-celled_, but the cells _bilocellate_.
[Illustration: Fig. 296. Stamen of Moonseed, with anther cut across;
this 4-celled, or rather 4-locellate.]
[Illustration: Fig. 297. Stamen of Pentstemon pubescens; the two
anther-cells diverging, and almost confluent.]
[Illustration: Fig. 298. Stamen of Mallow; the anther supposed to answer
to that of Fig. 297, but the cells completely confluent into one.]
[Illustration: Fig. 299. Stamen of Globe Amaranth; very short filament
bearing a single anther-cell; it is open from top to bottom, showing the
pollen within.]
[Illustration: Fig. 300-305. Stamens of several plants of the Labiate or
Mint Family. Fig. 300. Of a Monarda: the two anther-cells with bases
divergent so that they are transverse to the filament, and their
contiguous tips confluent, so as to form one cell opening by a
continuous line. Fig. 301. Of a Calamintha: the broad connective
separating the two cells. Fig. 302. Of a Sage (Salvia Texana); with long
and slender connective resembling forks of the filament, one bearing a
good anther-cell; the other an abortive or poor one. Fig. 303. Another
Sage (S. coccinea), with connective longer and more thread-shaped, the
lower fork having its anther-cell wholly wanting. Fig. 304. Of a White
Sage, Audibertia grandiflora; the lower fork of connective a mere
vestige. Fig. 305. Of another White Sage (A. stachyoides), the lower
fork of connective suppressed.]
291. But anthers may become _one-celled_, and that either by confluence
or by suppression.
292. By confluence, when the two cells run together into one, as they
nearly do in most species of Pentstemon (Fig. 297), more so in Monarda
(Fig. 300), and completely in the Mallow (Fig. 298) and all the Mallow
family.
293. By suppression in certain cases the anther may be reduced to one
cell or halved. In Globe Amaranth (Fig. 299) there is a single cell
without vestige of any other. Different species of Sage and of the White
Sages of California show various grades of abortion of one of the
anther-cells, along with a singular lengthening of the connective (Fig.
302-305).
294. The splitting open of an anther for the discharge of its pollen is
termed its _Dehiscence_.
[Illustration: Fig. 306. Stamen with the usual dehiscence of anther down
the side of each cell.]
[Illustration: Fig. 307. Stamen of Pyrola; cells opening by a terminal
hole.]
[Illustration: Fig. 308. Stamen of Barberry; cells of anther each
opening by an uplifted valve.]
295. As the figures show, this is commonly by a line along the whole
length of each cell, either lateral or, when the anthers are extrorse,
often along the outer face, and when introrse, along the inner face of
each cell. Sometimes the opening is only by a chink, hole, or pore at
the top, as in the Azalea, Pyrola (Fig. 307), etc.; sometimes a part of
the face separates as a sort of trap-door (or valve), hinged at the top,
and opening to allow the escape of the pollen, as in the Sassafras,
Spice-bush, and Barberry (Fig. 308).
296. =Pollen.= This is the powdery matter, commonly of a yellow color,
which fills the cells of the anther, and is discharged during
blossoming, after which the stamens generally fall or wither away. Under
the microscope it is found to consist of grains, usually round or oval,
and all alike in the same species, but very different in different
plants. So that the plant may sometimes be recognized from the pollen
alone. Several forms are shown in the accompanying figures.
[Illustration: Fig. 309. Magnified pollen of a Lily, smooth and oval;
310, of Echinocystis, grooved lengthwise; 311, of Sicyos, with bristly
points and smooth bands; 312, of Musk Plant (Mimulus), with spiral
grooves; 313, of Succory, twelve-sided and dotted.]
297. An ordinary pollen-grain has two coats; the outer coat thickish,
but weak, and frequently adorned with lines or bands, or studded with
points; the inner coat is extremely thin and delicate, but extensible,
and its cavity when fresh contains 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.]