A stamen is opposite each sepal, and in the centre of the flower is the rudiment of a pistil.
Similarly in the sporophylls of some cycads the bundles are endarch near the base and mesarch near the distal end of the stamen or carpel.
It sometimes happens that a single stamen is longer than all the rest.
POLLINATION, in botany, the transference of the pollen from the stamen to the receptive surface, or stigma, of the pistil of a flower.
- Stamen of Asclepias, showing filament f, anther a, and appendages p. Enlarged.
The function of the stamen is the development and distribution of the pollen.
And finally, we find flowers consisting of a single stamen with a bract.
The pollen-bearer or stamen and the ovule-bearer or car pel.
- Stamen, consisting of a filament (stalk) f and an anther a, containing the pollen p, which is discharged through slits in the two lobes of the anther.
The number of stamens is indicated by the Greek numerals prefixed to the term androus; thus a flower with one stamen is monandrous, with two, three, four, five, six or many stamens, di-, tri-, tetr-, pent-, hexor polyandrous, respectively.
C, Calyx; p, petal; e, stamen; s, stigmas.
Young stamen is abortive, flower in which the stigma (N) is receptive and cannot perform and the stamens (3) have not yet opened; its functions.
In Scrophularia the fifth stamen appears in the form of a scale; and in many Pentstemons it is reduced to a filament with hairs or a shrivelled membrane at the apex.
- Stamen of Lady's Mantle (Alchemilla), with the anther opening transversely.
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.
The inflorescence is a very simple one, consisting of one or two male flowers each comprising a single stamen, and a female flower comprising a flask-shaped pistil.
In Scrophularia the fifth stamen appears as a scale-like body; in other Scrophulariaceae, as in Pentstemon, it assumes the form of a filament, with hairs at its apex in place of an anther.
- Stamen of a species of Nightshade (Solanum), showing the divergence of the anther-lobes at the base, and the dehiscence by pores at the apex.
- The stamen of the Barberry (Berberis vulgaris), showing one of the valves of the anther (v) curved upwards, bearing the pollen on its inner surface.
For when the older morphologists spoke of a stamen as a metamorphosed leaf, it was implied that it originated as a foliage-leaf and subsequently became a stamen.
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 phylogeny of the various floral leaves, for instance, was generally traced as follows: foliage-leaf, bract, sepal, petal, stamen and carpel (sporophylls)in accordance with what Goethe termed ascending metamorphosis.
E, Spur of the label e, The fertile stamen, with lum.
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.
(For further details on the form and arrangement of the flower and its parts, see Flower.) Each stamen generally bears four pollen-sacs (microsporangia) which are associated to form the anther, and carried up on a stalk or filament.
Metamorphosis.It has already been pointed out that each kind of member of the body may present a variety of forms. For example, a stem may be a tree-trunk, or a twining stem, or a tendril, or a thorn, or a creeping rhizome, or a tuber; a leaf may be a green foliage-leaf, or a scale protecting a bud, or a tendril, or a pitcher, or a floral leaf, either sepal, petal, stamen or carpel (sporophyll); a root may be a fibrous root, or a swollen tap-root like that of the beet or the turnip. All these various forms are organs discharging some special function, and are examples of what Wolff called modification, and Goethe metamorphosis.
In most orchids the only stamen developed to maturity is the posterior one of the three opposite to the lip (anterior before the twisting of the ovary), the other two, as well as all three inner ones, being entirely absent, or present only in the form of rudiments.
The yellow stamen-bearing flowers are in sessile, nearly spherical catkins; the fertile ones vary in colour, from red or purple to greenish-white, in different varieties; the erect cones, which remain long on the branches, are above an inch in length and oblong-ovate in shape, with reddish-brown scales somewhat waved on the edges, the lower bracts usually rather longer than the scales.
As a matter of fact, a stamen is a stamen and nothing else, from the very beginning.
The details of the structure of the flower show a wide variation; the flowers are often extremely simple, sometimes as in Arum, reduced to a single stamen or pistil.
The long connective of the single stamen is hinged to the short filament and has a shorter arm ending in a blunt process and a longer arm bearing a half-anther.