Democratic Sentinel, Volume 6, Number 14, Rensselaer, Jasper County, 5 May 1882 — Movements of Leaves. [ARTICLE]

Movements of Leaves.

Leaves, Mr. Darwin says, when they go to sleep, move either upward or downward; or in the case of the leaflets of compound leaves, forward—that is, towards the apex of the leaf or backwards, that iB, towards its base; or again, they may rotate on their own axis without moving either upwards or downwards; but iu almost every case the plane of the blade is so placed as to stand nearly or quite vertically at night. Moreover, the upper surfaoe of each leaf, and more especially of each leaflet, is often brought into close contact with that of the opposite one, as the upper surfaces appear to require more protection than the lower. The evil effects which result if sleeping leaflets be prevented from pressing their upper surfaces together, so as to protect them from radiation, were well seen in experiments of Mr. Darwin, in which he pressed down the leaflets of oxaliß, marsilia, etc., so that they could not bring their upper surfaces into contract; the result was that the leaves were killed. Thus of twenty-four leaves of marsilia extended horizontally, exposed to the zenith and to obstructed radiation, twenty were killed and one injured, whilst a relatively very small proportion of the leaves which had been allowed to go to sleep with their leaflets vertically dependent were killed or injured. Mr. Darwin noticed that the difference in the amount of dew on the pinned-open leaflets and on those which had gone to sleep was generally conspiouous, the latter being sometimes absolutely dry, whilst the leaflets which had been horizontal were coated with large beads of dew. Another fact observable was that when leaves were kept motionless they are more liable to injury than when they were slightly waved about by the wind, and thus got a little warmed by tba surrounding air.