File:The natural history of plants, their forms, growth, reproduction, and distribution; (1902) (14765855835).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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ut. As long as the fruit is unripe such expansion isprevented by the tense tissue close to the stalk, but with the ripening of the fruitthis obstacle is removed. The fruit then severs itself from the conical end of thestalk and at the same moment the expansion of the strained layer of tissue takesplace. The consequence is that the interior of the fruit is subjected to greatpressure, and the seeds, together with the surrounding mucilage, are squirted out SLING-FRUITS. 833 with considerable force through the hole which was previously closed by the endof the stalk (see fig. 458 2). The Dorsteniacese behave in a manner no less remarkable. As in the ca.se ofFigs so also in these plants, numbers of small flowers are seated upon an enlargedreceptacle, which remains fleshy and succulent after the small one-seeded fruits havedeveloped from the flowers. The lower portion of each fruit has thick walls, and isembedded in the receptacle like a hair-follicle in the human skin, whilst the delicat*;-
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Fig. 459.—Sling-fruits. > Orobus vernus. - and s Geranium palustre. ■* Viola elatior. * Cardamine impalieiis. and 8 Acanthus mollis. 9 and lo Ricinus communis. Impatieiis Solitangtrt coated portion projects above the receptacle in the form of a papilla. When theseed is quite ripe the turgidity of the outer cellular layer of the thick wall of thefruit increases, the thin-walled top is torn, the thick walls suddenly close, and theseed hitherto enveloped by them is violently ejected. A special case of the expulsion of seeds as from a sling is also found in Oxali-dacese, of which the common Wood-sorrel (Oxalis Acetosella, see figs. 458 ^- *• ^) maybe taken as an example. In this case it is the seed-coat that possesses a specialtumescent tissue adapted to the expulsion of the seeds. One of the deeper layersof the seed-coat is composed of tense cells and is itself in a highly strained condition, 836 THE DISPERSION OF SPECIES BY MEANS OF FRUITS AND SEEDS. whilst the outer laj^ers of

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