Axillary or terminal spikes; they have four stamens, which bear at the back four small herbaceous petal-like structures, and four free carpels, which ripen to form four small green fleshy fruits, each containing one seed within a hard inner coat;.
The catkins of the poplars differ from those of the nearly allied willows in the presence of a rudimentary perianth, of obliquely cup-shaped form, within the toothed bracteal scales; the male flowers contain from eight to thirty stamens; the fertile bear a onecelled (nearly divided) ovary, surmounted by the deeply cleft stigmas; the two-valved capsule contains several seeds, each furnished with a long tuft of silky or cotton-like hairs.
The spores, as in the heterosporous Pteridophyta, are of two kindsmicrospores (pollen grains) borne in microsporangia (pollen sacs) on special leaves (sporophylls) known as stamens, and macrospores (embryo-sac) borne in macrosporangia (ovules) on sporophylls known as carpels.
The sporophylls (stamens and carpels) are generally associated with other leaves, known as the perianth, to form a flower; these subsidiary leaves are protective and attractive in function and their development is correlated with the transport of pollen by insect agency (see ANGI0sPERM5; POLLINATION, and FLOWER).
In some orders the parts are numerous, chiefly in the case of the stamens and the carpels, as in the buttercup and other members of the order Ranunculaceae.
There is a very wide range in the general structure and arrangement of the parts of the flower, associated with the means for ensuring the transference of pollen; in the simplest cases the flower consists only of a few stamens or carpels, with no enveloping sepals or petals, as in the willow, while in, the more elaborate type each series is represented, the whole forming a complicated structure closely correlated with the size, form and habits of the pollinating agent (see Flower).
Within the perianth, and springing from its sides, or apparently from the top of the ovary, are six stamens whose anthers contain pulverulent pollen-grains.
These stamens encircle a style which is the upward continuation of the ovary, and which shows at its free end traces of the three originally separate but now blended carpels of which the ovary consists.
Described, but with the ovules on the walls of the cavity (not in its axis or centre), a six-parted perianth, a stamen or stamens and stigmas.
In place of the six stamens we commonly find but one (two in Cypripedium), and that one is raised together with the stigmatic surfaces on an elongation of the floral axis known as the "column."
It would appear, then, that the orchid flower differs from the more general monocotyledonous type in the irregularity of the perianth, in the suppression of five out of six stamens, and in the union of the one stamen and the stigmas.
Floral diagram of typical orchid flower; 1, labellum; a, anther; s, rudiments of barren stamens (staminodes).
The order is divided into two main groups based on the number of the stamens and stigmas.
The first Diandreae, has two or rarely three fertile stamens and three functional stigmas.
In Cypripedium two stamens are present, one on each side of the column instead of one only at the top, as in the group Monandreae, to which belong the remaining genera in which also only two stigmas are fertile.
What may be considered the normal number of stamens is, as has been said, six, arranged in two rows.
In Cypripedium two of the outer stamens are wanting; the third - the one, that is, which corresponds to the single fertile stamen in the Monandreae - forms a large sterile structure or staminode; the two lateral ones of the inner series are present, the third being undeveloped.
The letter L indicates the position of the labellum; the large figures indicate the developed stamens; the italic figures show the position of the suppressed stamens.
I 4 5 6 2 L 3 2 L 3 Arrangement of stamens Arrangement of stamens in Orchis.
Many Thomisidae lurk amongst the stamens and petals of flowers, which they closely match in colour, waiting to seize the insects which visit the blossoms for nectar.
The flowers, which are borne in the leaf-axils at the ends of the stem, are very handsome, the six, generally narrow, petals are bent back and stand erect, and are a rich orange yellow or red in colour; the six stamens project more or less horizontally from the place of insertion of the petals.
The five stamens alternate in position with the lobes of the corolla.
And Sambucus, more rarely two-lipped as in Lonicera; the sepals and petals are usually five in number and placed above the ovary, the five stamens are attached to the corolla-tube, there are three to five carpels, and the fruit is a berry as in honeysuckle or snowberry (Symphoricarpus), or a stone fruit, with several, usually three, stones, as in Sambucus.
The flowers are regular, with four free sepals arranged in two pairs at right angles, four petals arranged crosswise in one series, and two sets of stamens, an outer with two members and an inner with four, in two pairs placed in the middle line of the flower and at right angles to the outer series.
The four inner stamens are longer than the two outer; and the stamens are hence collectively described as tetradynamous.
The petals are generally white or yellow, more rarely lilac or some other colour, and between the bases of the stamens are honey-glands.
Owing, however, to the close proximity of stigma and anthers, very slight irregularity in the movements of the visiting insect will cause self-pollination, which may also occur by the dropping of pollen from the anthers of the larger stamens on to the stigma.
- Two Stamens of Viola tricolor (Pansy), with their two anther lobes and the processp extending beyond them.
One of the stamens has been deprived of its spur; the other shows its spur, c. a row down the centre, are shot out to some little distance from she parent plant.
B, pair of bracteoles below the flower; s, sepals; p, petals; st, stamens; o, ovary.
5), the perianth which is generally petaloid occupying the two outer whorls, followed by two whorls of stamens, with a superior ovary of three carpels in the centre of the flower; the ovary is generally three-chambered and contains an indefinite number of anatropous ovules on axile placentas (see fig.
Evergreen shrub with flattened leaf-like cladodes, native in the southerly portion of England and Wales; the small flowers are unisexual and borne on the face of the cladode; the male contains three stamens, the filaments of which are united to form a short stout column on which are seated the diverging cells of the anthers; in the female the ovary is enveloped by a fleshy staminal tube on which are borne three barren anthers.
Terminating the short annual shoot which bears a whorl of four or more leaves below the flower; in this and in some species of the nearly allied genus Trillium (chiefly temperate North America) the flowers have a fetid smell, which together with the dark purple of the ovary and stigmas and frequently also of the stamens and petals, attracts carrion-loving flies, which alight on the stigma and then climb the anthers and become dusted with pollen; the pollen is then carried to the stigmas of another flower.
The parts of the flower are in fives in calyx, corolla and stamens, followed by two carpels which unite to form a superior ovary.
The slender filaments of the stamens vary widely, often in the same flower; the anthers are linear to ovate in shape, attached at the back to the filament, and open lengthwise.
Each has a small calyx in the form of a shallow rim, sometimes five-lobed or toothed; five petals, which cohere by their tips and form a cap or hood, which is pushed off when the stamens are ripe; and five free stamens, placed opposite the petals and springing from a fleshy ring or disk surrounding the ovary; each bears a twocelled anther.
The anomalous position of the stamens in front of the petals is explained by the abortion or non-development of an outer row of stamens, indications of which are sometimes seen on the hypogynous disk encircling the ovary.
The cultivated vine has usually hermaphrodite flowers; but as it occurs in a wild state, or as an escape from cultivation, the flowers manifest a tendency towards unisexuality: that is, one plant bears flowers with stamens only, or only the rudiments of the pistil, while on another plant the flowers are bisexual.
Exclusively female flowers without stamens do not appear to have been observed.
The perianth consists of five or six oblong greenish lobes, within which is found a tuft, consisting of a large number of stamens, each of which has a very short filament and an oblong two-lobed anther bursting longitudinally, and surmounted by an oblong lobe, which is the projecting end of the connective.
The flowers are regular, with a perianth springing from above the ovary, tubular below, with spreading segments and a central corona; the six stamens are inserted within the tube.
In the male flowers, which are numerous, the stamens are sixteen in number and arranged in pairs; the female flowers are solitary, with traces of stamens, and a smooth ovary with one ovule in each of the eight cells - the ovary is surmounted by four styles, which are hairy at the base.
Each male flower consists of a small scale or bract, in the axil of which are usually two, sometimes three, rarely five stamens, and still more rarely a larger number.
Increase in size upwards, and at length become crowded, numerous and petaloid, forming a funnel-shaped blossom, the beauty of which is much enhanced by the multitude of conspicuous stamens which with the pistil occupy the centre.
The sepals and petals are free or more or less united, the stamens as many or twice as many as the petals; the carpels, usually free, are equal to the petals in number, and form in the fruit follicles with two or more seeds.
The system of Linnaeus was founded on characters derived from the stamens and pistils, the so-called sexual organs of the flower, and hence it is often called the sexual system.
Nehemiah Grew seems to have been the first to describe, in a paper on the Anatomy of Plants, read before the Royal Society in November 1676, the functions of the stamens and pistils.
Grew speaks of the attire, or the stamens, as being the male parts, and refers to conversations with Sir Thomas Millington, Sedleian professor at Oxford, to whom the credit of the sexual theory seems really to belong.
Camerarius, professor of botany and medicine at Tubingen, published a letter on the sexes of plants, in which he refers to the stamens and pistils as the organs of reproduction, and states the difficulties he had encountered in determining the organs of Cryptogamic plants.
In the latter division of plants he could not detect stamens and pistils, and he did not investigate the mode in which their germs were produced.