File:On the Irritability of the Fronds of Asplenium bulbiferum, With Special Reference to Graviperception (1922) (14803278903).jpg

Identifier: philtrans01489273 (find matches)
Title: On the Irritability of the Fronds of Asplenium bulbiferum, With Special Reference to Graviperception
Year: 1922 (1920s)
Authors: Prankerd, T.
Subjects: Proceedings of the Royal Society of London Philosophical Transactions of the Royal Society
Publisher: Royal Society of London

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en the first presentation of the stimulus and the beginningof the response. + The time elapsing between the first presentation of the stimulus and the end ofthe reaction. % The -duration of these periods is now under investigation by my student, MissF. M. O. Waight. § The subsequent relatively slight hyponasty is included here for convenience underthe term epinasty. Fronds of Asplenium bulbiferum. 147 inception of the frond, and is represented towards the end of the secondphase higher than gravity or light, since its effect at this time is more pro-nounced than either, and seems to dominate the situation. It ceases at aperiod somewhere near the complete uncurling of the frond, but which variesgreatly with the individual. Indeed, the last curve must be taken as evenmore approximate than either of the others, since epinasty is very variable,both in amplitude and the time of appearance and disappearance of itsremarkable expression towards the end of the second phase. Z^ phase 3^-d phase
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Fig. 4.—For explanation,see text. It is important for our purpose that the time at which geotropic irritabilityceases should be ascertained as nearly as possible, but in actual practice thisis very difficult, as the hyponastic curve is apt to simulate that due togeotropism, and the matter is complicated by the individual variability ofthe frond, which is most apparent in the very unstable adolescent stage. Itseems at least certain that growth continues after the cessation of geotropicirritability, the frond being at this time only 70-80 per cent, of the lengthfinally attained. The fern frond is in many ways the biological equivalent of the angio-spermic shoot, and, like it, will bring itself back into the vertical should it bedisplaced from this position. It accomplishes this by passing the verticaland swinging like a pendulum backwards and forwards till it remains uprightin a manner similar to that well known for flowering plants, and originally, Ibelieve, described by Darwin ((2),philtrans01489273

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