unable to sleep at night.  It was therefore moderately watered, as well as syringed, late in the evening.  On the next morning (30th) the bush looked as fresh as ever, and at night the leaves went to sleep.  It may be added that a small branch while growing on the bush was enclosed, by means of a curtain of bladder, during 13 days in a large bottle half full of quicklime, so that the air within must have been intensely dry; yet the leaves on this branch did not suffer in the [page 338] least, and did not close at all during the hottest days.  Another trial was made with the same bush on August 2nd and 6th (the soil appearing at this latter date extremely dry), for it was exposed out of doors during the whole day to the wind, but the leaflets showed no signs of closing.  The Chilian form therefore differs widely from the one at Würzburg, in not closing its leaflets when suffering from the want of water; and it can live for a surprisingly long time without water.

Tropaeolum majus (?) (cultivated var.) (Tropaeoleae).—­Several plants in pots stood in the greenhouse, and the blades of the leaves which faced the front-lights were during the day highly inclined and at night vertical; whilst the leaves on the back of the pots, though of course illuminated through the roof, did not become vertical at night.  We thought, at first, that this difference in their positions was in some manner due to heliotropism, for the leaves are highly heliotropic.  The true explanation, however, is that unless they are well illuminated during at least a part of the day they do not sleep at night; and a little difference in the degree of illumination determines whether or not they shall become vertical at night.  We have observed no other so well-marked a case as this, of the influence of previous illumination on nyctitropic movements.  The leaves present also another peculiarity in their habit of rising or awaking in the morning, being more strongly fixed or inherited than that of sinking or sleeping at night.  The movements are caused by the bending of an upper part of the petiole, between ½ and 1 inch in length; but the part close to the blade, for about 1/4 of an inch in length, does not bend and always remains at right angles to the blade.  The bending portion does not present any external or internal difference in structure from the rest of the petiole.  We will now give the experiments on which the above conclusions are founded.

A large pot with several plants was brought on the morning of Sept. 3rd out of the greenhouse and placed before a north-east window, in the same position as before with respect to the light, as far as that was possible.  On the front of the plants, 24 leaves were marked with thread, some of which had their blades horizontal, but the greater number were inclined at about 45o, beneath the horizon; at night all these, without exception, became vertical.  Early on the following morning (4th) they reassumed their former positions, and at night again became vertical.