File:Text-book of structural and physiological botany (1877) (14753573836).jpg

Identifier: textbookofstruct00thom (find matches)
Title: Text-book of structural and physiological botany
Year: 1877 (1870s)
Authors: Thomé, Otto Wilhelm, 1840- Bennett, Alfred William, 1833-1902
Subjects: Plant physiology
Publisher: New York : J. Wiley & sons
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Biodiversity Heritage Library

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ses any irritationupon it. It is believed by some botanists that the objectof the capture of the insect is the nutrition of the plant.(The sensitive part in this case appears to consist of threesmall bristles on each half of the upper surface of the blade.) Closely connected with these movements are those be-longing to tendrils and tendril-like organs. In their earlystate, before they have coiled up backwards or have clungto a support, these organs are sensitive to simple and slightcontact or to very light rubbing, the side on which they aretouched becoming, after some minutes, concavely curved.The bent tendril subsequently straightens itself, and is thenagain irritable. Bent tendrils are sensitive only on the con-cave side. The stamen of many Compositae, such as Centaiwea., 204 Structural and Physiological Botany, contract when irritated before pollination. In this case thecells are probably altered in form by the contact, becom-ing shorter and broader. The stamens of Bei^heris^ when
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Fig. 372.—Venuss fly-trap, Dioncea muscipula (natural size). touched on the inner side, spring violently against the pistil,and place their anthers in contact with the stigma. The The Life of the Plant. 205 stamens of the grass of Parnassus, Parnassia pahcstris^lengthen in succession, and place their anthers on thestigma. The stigmas of some plants, as Bignonia^ Gratiola^Martinia, \_Minmlus\ &c., which are expanded at the timeof pollination, close on contact. A similar phenomenon isexhibited by the stigmas of Torenia asiatica, which closeimmediately after pollination, open again in a few days, butare then insensitive to further contact. A fuller discussionof the mechanism of these movements would take too muchspace; but with regard to their purpose, it is obvious thatthey are all closely connected with the sustenance and pro-pagation of the plant. Those parts of plants in which there is generally a ten-sion of the tissues exhibit a constant increase and decreasein the degree of

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