[260]

March 7th to morning of March 11th 1878

Pelargonium zonale. Nutation of Stems

A young plant 7 1/2 inches high, had glass filament fixed transversely 1/2 inch beneath leafy bud on summit, & movement of bead traced on horizontal glass — Tracing magnified 11 times as ascertained measured at close of observations.— Plant illuminated very feebly from above. In order to fix filament & see mark below I had to cut off 3 leaves on one side. The stem during whole of 7th & following night & till 11° on the 8th moved in nearly same general course) Next morning traced a little [illeg] in transversely to the light & to considerable distance & in only slight zig-zag line. Next morning (8th); & this was to side whence leaves had been cut off; but whether this was cause I know not.

Next morning stood trended a little more to the right & at 11° still more decidedly so.

At 8° a.m. (on the 8th) tracing copied (see fig.) after 11° changed its course a little & became very much more zig-zag. During night of 8th almost reversed its course. Next morning 9th moved short distance as shown till from 8' 7° to 10° a.m & then seemed to stand almost still for the stem had grown grown so much that tracing not sufficiently magnified, so I moved mark beneath, & (at 12° March 9th began new tracing.— A break will be seen in tracing where this occurred. Between 12° 5° P.m on 16th & 10° 30' P.m made more than a circle. Course during night & for an hour (viz from 7° to 8' am) on following morning (March 11th) shown in tracing.

There can be no doubt that plant, when accustomed to place & got over former former effects of light & apo-geotropism circumnutates.