On the Movements of Petals

Authors

Esther Pearl Hensel, University of Nebraska

Date of this Version

7-1905

Citation

UNIVERSITY STUDIES, VOL. V, JULY I905, No. 3

Abstract

The following paper has to do with an investigation of the physical causes· which bring about opening and closing movements, periodic or otherwise, of certain flowers. With that end in view, seven different species of flowering plants have been experimented upon directly, a much larger number being simply observed with respect to the nature, time, etc., of their anthotropic movements. Movement consists in the corolla taking upon itself either the open or closed position for certain periods of the day or night; for example, the morning glory (Ipomoea purpurea) opens early in the morning (from 4:00 to 5 :00 A.M., in the greenhouse) and closes from II :00 A.M. to 2 :00 P.M., or even 5:00 P.M. on cool days, while the common dandelion (Taraxacum taraxacum) opens from 7:00 to 8:00 A.M. and closes from 5 :00 to 6:00 P.M. In the closed position, the petals or florets may assume practically the same position ,as that of the bud, as in the gentians, asters, dandelions, etc.; often, however, the edges of the petals only touch, forming a dome inside of which the stamens and pistil are well protected, as in the wild rose and in the tulip. In some genera, as in Mentzelia, the sepals may stay reflexed after the first opening.

Following is a list of plants which show these movements, those preceded by a * having been experimented upon directly; the others were simply observed. The list is very small when compared with the cases actually known, since it simply includes those coming under personal observation within the last two or three years:

So much has been written on the subject of flower movement, and with such different views as to its cause, that it seems advisable to give a rather detailed account of the work of the different investigators.