§ 10. The Stamens

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108. Although in a few cases the outer stamens may gradually pass into petals, yet in general, Stamens are very different in shape and aspect from leaves, sepals or petals. It is only in a theoretical point of view (not the less important in the study of the physiological economy of the plant) that they can be called altered leaves.

109. The usual form is a stalk, called the filament, bearing at the top an anther divided into two pouches or cells. These anther-cells are filled with pollen, consisting of minute grains, usually forming a yellow dust, which, when the flower expands, is scattered from an opening in each cell. When the two cells are not closely contiguous, the portion of the anther that unites them is called the connectivum.

110. The filament is often wanting, and the anther sessile, yet still the stamen is perfect; but if the anther, which is the essential part of the stamen, is wanting, or does not contain pollen, the stamen is imperfect, and is then said to be barren or sterile (without pollen), abortive or rudimentary (84), according to the degree to which the imperfection is carried. Imperfect stamens are often called staminodia.

111. In unsymmetrical flowers, the stamens of each whorl are sometimes reduced in number below that of the petals, even to a single one, and in several Natural Orders they are multiplied indefinitely.

112. The terms monandrous and polyandrous are restricted to flowers which have really but one stamen, or an indefinite number respectively. When several stamens are united into one, the flower is said to be synandrous.

113. Stamens are

monadelphous, when united by their filaments into one cluster. This cluster either forms a tube round the pistil, or, if the pistil is wanting, occupies the centre of the flower.

diadelphous, when so united into two clusters or phalanges. The term is more especially applied to certain Leguminosæ, in which nine stamens are united in a tube slit open on the other side, and a tenth, placed in a slit, is free. In some other plants the stamens are equally distributed in the two clusters.

triadelphous, pentadelphous, polyadelphous, when so united into three, five, or many clusters or phalanges.

syngenesious, when united by their anthers in a ring round the pistil, the filaments usually remaining free.

didynamous, when (usually in a bilabiate flower) there are four stamens in two pairs, those of one pair longer than those of the other.

tetradynamous, when (in Cruciferæ) there are size, four of them longer than the two others.

exserted when longer than the corolla, or even when longer than its tune, if the limb be very spreading.

114. An Anther (109) is

adnate, when continuous with the filament, the anther-cells appearing to lie their whole length along the upper part of the filament.

innate, when firmly attached by their base to the filament. This is an adnate anther when rather more distinct from the filament.

versatile, when attached by their back to the very point of the filament, so as to swing loosely.

115. Anther-cells may be parallel or diverging at a less or greater angle; or divaricate, when placed end to end as to form one straight line. The end of each anther-cell placed nearest to the other cell is generally called its apex or summit, and the other end its base (36); but some botanists reverse the sense of these terms.

116. Anthers have often, on their connectivum of cells, appendages termed bristles (setæ), spurs, crests, points, glands, etc., according to their appearance.

117. Anthers have occasionally only one cell : this make take place either by the disappearance of the partition betweein two closely contiguous cells, when these cells are said to be confluent; or by the abortion or total deficiency of one of the cells, when the anther is said to be dimidiate.

118. Anthers will open or dehisce to let out the pollen, like capsules, in valves, pores, or slits. Their dehiscence is introrse, when the opening faces the pistil; extrose, when towards the circumference of the flower.

119. Pollen (109) is not always in the form of dust. It is sometime collected in each cell into one or two little wax-like masses. Special terms used in describing these masses or other modification of the pollen will be explained under the Orders where they occur.

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