Oxalis Plumierii.--In this species the three leaflets do not surround the
summit of the petiole, but the terminal leaflet projects in the line of the
petiole, with a lateral leaflet on each side. They all sleep by bending
vertically downwards, but do not become at all folded. The petiole is
rather long, and, one having been secured to a stick, the movement of the
terminal leaflet was traced during 45 h. on a vertical glass. It moved in a
very simple manner, sinking rapidly after 5 P.M., and rising rapidly early
next morning. During the middle of the day it moved slowly and a little
laterally. Consequently the ascending and descending lines did not
coincide, and a single great ellipse was formed each day. There was no
other evidence of circumnutation, and this fact is of interest, as we shall
hereafter see.
Oxalis sensitiva.--The leaflets, as in the last species, bend vertically
down at night, without becoming folded. The much elongated main petiole
rises considerably in the evening, but in
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some very young plants the rise did not commence until late at night.
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