Encyclopaedia Britannica, 11th Edition, Slice 5 Volume 10

Encyclopaedia Britannica, 11th Edition, Slice 5 Volume 10

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Excerpt: ...glumes; c, fertile glumes, each enclosing one flower with its pale, d; the zigzag axis (rhachilla) bears long silky hairs. Hairs, scales, teeth or processes of different kinds are sometimes times developed on the filament. In spiderwort (Tradescantia virginica) the hairs are beautifully coloured, moniliform or necklace-like, and afford good objects for studying rotation of the protoplasm. Filaments are usually articulated to the thalamus or torus, and the stamens fall off after fertilization; but in Campanula and some other plants they are continuous with the torus, and the stamens remain persistent, although in a withered state. Changes are produced in the whorl of stamens by cohesion of the filaments to a greater or less extent, while the anthers remain free; thus, all the filaments of the androecium may unite, forming a tube round the pistil, or a central bundle when the pistil is abortive, the stamens becoming monadelphous, as occurs in plants of the Mallow tribe; or they may be arranged in two bundles, the stamens being diadelphous, as in Polygala, Fumaria and Pea; in this case the bundles may be equal or unequal. It frequently happens, especially in Papilionaceous flowers, that out of ten stamens nine are united by their filaments, while one (the posterior one) is free (fig. 68). When there are three or more bundles the stamens are triadelphous, as in Hypericum aegyptiacum, or polyadelphous, as in Ricinus communis (castor-oil). In some cases, as in papilionaceous flowers, the stamens cohere, having been originally separate, but in most cases each bundle is produced by the branching of a single stamen. When there are three stamens in a bundle we may conceive the lateral ones as of a stipulary nature. In Lauraceae there are perfect stamens, each having at the base of the filament two abortive stamens or staminodes, which may be analogous to stipules. Filaments sometimes are adherent to the pistil, forming a column (gynostemium), as in...show more

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  • Paperback
  • 189 x 246 x 10mm | 340g
  • Rarebooksclub.com
  • United States
  • English
  • black & white illustrations
  • 1236715667
  • 9781236715661