Volume 4

The natural history of plants : their forms, growth, reproduction, and distribution / from the German of Anton Kerner von Marilaun ; translated and edited by F.W. Oliver, with the assistance of Marian Busk and Mary F. Ewart ; with about 2000 original woodcut illustrations and sixteen plates in colours.

  • Kerner von Marilaun, Anton, 1831-1898.
Date:
1897
Catalogue details

Licence: Public Domain Mark

Credit: The natural history of plants : their forms, growth, reproduction, and distribution / from the German of Anton Kerner von Marilaun ; translated and edited by F.W. Oliver, with the assistance of Marian Busk and Mary F. Ewart ; with about 2000 original woodcut illustrations and sixteen plates in colours. Source: Wellcome Collection.

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    Fig. 290.—Flower of the Rue (Ruta gra- veolens) x 3. (After Baillon.) elongate, and thus assume a position overhanging the honey receptacles, where they are inevitably brushed by insects. For the tenth group we may select the Rue (Ruta; see fig. 290) as an example. The flower contains ten anthers supported by stiff filaments, arranged in the form of a star. First, one of these filaments bends up and places its anther in the middle of the flower, just in the way to the fleshy ring which secretes nectar at the base of the pistil: it remains there about a day, and then bends back and resumes its former position. While the first stamen is bending back, a second rises up and undergoes the same movements. And so it goes on until the ten anthers have all stood in the centre of the flower in turn and discharged their pollen there. When, finally, the last stamen has bent back again, the stigma, which has meanwhile matured, is seen in the centre of the flower where the anthers have successively shed their pollen. A process which is closely connected with the interchange of position of anthers and stigmas, in bringing about cross-fertilization between herma- phrodite flowers, is the separation and subsequent falling away of the stigmas when the surrounding anthers begin to dehisce. We may take one of the Urticaceae, the Wall Pellitory (Parietaria; see figs. 291 2> 3i 4), as a type of this. The stigma is always developed before the flowers open in this plant, and at the commencement of the flowering period it may be seen projecting like a dusting-brush from the green flower-bud (fig. 2913). The curved anther- filaments are at this time coiled like watch-springs and covered over by the as yet unopened floral-leaves. Before these filaments jerk up and scatter their pollen the stigma withers and shrivels up and the style becomes detached from the ovary. It falls off with the dried-up stigma, so that, when the pollen is liberated from the anthers, the ovary is terminated merely by a small stump which is really the withered remnant of the fallen style (fig. 2914). The falling of the anthers and stamens at the time when the adjoining stigmas become mature is of much more frequent occurrence than the detachment and falling of the stigmas before the pollen is shed. In the flowers of Balsams (Im- patiens glandulosa, Nolitangere, tricornis, &c.) the anthers are united into a kind of cap which arches over the stigma. As soon as the flower has opened and become accessible to flying insects, the anthers dehisce and only the cap which they form can be seen at the entrance to the flower. Later, the filaments of the anthers become detached, and the anther-cap falls out of the flower; only the stigma, which has meanwhile matured, is now visible in the middle of the flower. The large-flowered species of Crane’s-bill (e.g. Geranium argenteum, pratense, sylvati- cum\ see fig. 291 J) have a similar arrangement. Two of the anthers which have hitherto been covered by the petals dehisce almost simultaneously with the opening of the flower; the others then open in a certain order and expose their pollen in