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Page:Popular Science Monthly Volume 18.djvu/524

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THE POPULAR SCIENCE MONTHLY.

ment was so simple that it is not worth while to give the diagram. The leaflet fell slowly from the early morning till about 1 p. m. It then rose gradually at first, but rapidly late in the evening. It occasionally stood still for some twenty minutes during the day, and sometimes zigzagged a little.

PSM V18 D524 Coronilla rosea leaf asleep.jpg
Fig. 11.—Coronilla rosea: Leaf asleep.

The leaves of Coronilla rosea bear nine or ten pairs of opposite leaflets, which during the day stand horizontally, with their midribs at right angles with the petiole. At night they rise up, so that the opposite leaflets come nearly into contact, and those on the younger

PSM V18 D524 Desmodium gyrans in diurnal and nocturnal state.jpg
Fig. 12.—Desmodium gyrans: A, stem during the day; B, stem with leaves asleep. Copied from a photograph; figures reduced.

leaves into close contact. At the same time they bend back toward the base of the petiole until their midribs form with it angles of from 40° to 50° in a vertical plane (as in Fig. 11),

The appearance presented by a sleeping branch of Desmodium gyrans and by one in the daytime, copied from two photographs, is