File:The natural history of plants, their forms, growth, reproduction, and distribution; (1902) (14785676303).jpg

Identifier: naturalhistoryof02kern (find matches)
Title: The natural history of plants, their forms, growth, reproduction, and distribution;
Year: 1902 (1900s)
Authors: Kerner von Marilaun, Anton, 1831-1898 Oliver, Francis Wall, 1864- Macdonald, Mary Frances Ewart Busk, Marian Balfour, Lady
Subjects: Botany
Publisher: London, Blackie
Contributing Library: NCSU Libraries
Digitizing Sponsor: NCSU Libraries

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integuments inclosed in a flask-shaped perianth. On ripening, the perianth becomes fleshy, and the outer integu-ment of the ovule hardens to a stone. There are 15 species, distributed in thetropics. Welwitschia mirabilis is a plant altogether unique. Discovered some thirty-five years ago by the botanical explorer Welwitsch, it has formed the subject of aclassical monograph by Hooker. It occurs in the desert regions of West TropicalAfrica (Angola, Damaraland, &c.). The stem is dwarf and top-shaped (cf. fig. 411),and may attain more than a metre in diameter. The summit of the plant ne\erreaches far above the surface, and it bears two huge leathery leaves which sprawlon the sand on either hand. Actually 4 leaves are produced, the 2 cotyledons,which fall away whilst the plant is still quite young, and an additional pair placedat right angles to the cotyledons and persisting throughout the life of the plant.These 2 leaves grow continually at the base whilst their apical regions become
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728 THE SUBDIVISIONS OF THE VEGETABLE KINGDOM. tattered and broken. Wehvitschia, once established, does not increase much inlength but continually in thickness. From the edge of its disc, in the leaf-axils,arise branches which bear cones (cf. fig. 411). The male cones are small, and in theaxils of their scales occur flowers consisting of 6 stamens united together into asheath and surrounding a central structure which resembles an ovary, and containsa single ovule, which is, however, so far as is known, always abortive. This ovary-like structure is provided with a trumpet-like stigma , and the occurrence of thisremarkable structure in the male flowers points to the fact that the ancestors ofthis plant possessed hermaphrodite flowers. The fertile female flowers occur in theaxils of the scales of other much larger cones, which become bright red in colour.Each flower consists of a perianth containing an ovule with 2 integuments, butalthough the inner of these integuments is very long, the

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