were traced.  It is troublesome to observe the movements of leaves in the middle of the night, but this was done in a few cases; and tracings were made during the early part of the night of the movements in the case of Oxalis, Amphicarpaea, two species of Erythrina, a Cassia, Passiflora, Euphorbia and Marsilea; and the leaves after they had gone to sleep, were found to be in constant movement.  When, however, opposite leaflets come into close contact with one another or with the stem at night, they are, as we believe, mechanically prevented from moving, but this point was not sufficiently investigated.

When the movements of sleeping leaves are traced during twenty-four hours, the ascending and descending lines do not coincide, except occasionally and by accident for a short space; so that with many plants a [page 404] single large ellipse is described during each twenty-four hours.  Such ellipses are generally narrow and vertically directed, for the amount of lateral movement is small.  That there is some lateral movement is shown by the ascending and descending lines not coinciding, and occasionally, as with Desmodium gyrans and Thalia dealbata, it was strongly marked.  In the case of Melilotus the ellipses described by the terminal leaflet during the day are laterally extended, instead of vertically, as is usual; and this fact evidently stands in relation with the terminal leaflet moving laterally when it goes to sleep.  With the majority of sleeping plants the leaves oscillate more than once up and down in the twenty-four hours; so that frequently two ellipses, one of moderate size, and one of very large size which includes the nocturnal movement, are described within the twenty-four hours.  For instance, a leaf which stands vertically up during the night will sink in the morning, then rise considerably, again sink in the afternoon, and in the evening reascend and assume its vertical nocturnal position.  It will thus describe, in the course of the twenty-four hours, two ellipses of unequal sizes.  Other plants describe within the same time, three, four, or five ellipses.  Occasionally the longer axes of the several ellipses extend in different directions, of which Acacia Farnesiana offered a good instance.  The following cases will give an idea of the rate of movement:  Oxalis acetosella completed two ellipses at the rate of 1 h. 25 m. for each; Marsilea quadrifoliata, at the rate of 2 h.; Trifolium subterraneum, one in 3 h. 30 m.; and Arachis hypogaea, in 4 h. 50 m.  But the number of ellipses described within a given time depends largely on the state of the plant and on the conditions to which it is exposed.  It often happens that a single ellipse may be described during one [page 405] day, and two on the next.  Erythrina corallodendron made four ellipses on the first day of observation and only a single one on the third, apparently owing to having been kept not sufficiently illuminated and perhaps not warm enough.  But there seems likewise to be an innate tendency in different species of the same genus to make a different number of ellipses in the twenty-four hours:  the leaflets of Trifolium repens made only one; those of T. resupinatum two, and those of T. subterraneum three in this time.  Again, the leaflets of Oxalis Plumierii made a single ellipse; those of O. bupleurifolia, two; those of O. Valdiviana, two or three; and those of O. acetosella, at least five in the twenty-four hours.