clearly displayed, as shown in the following cases:--A seedling was placed
in front and near a north-east window with a line joining the
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two cotyledons parallel to the window. It was thus left the whole day so as
to accommodate itself to the light. On the following morning a filament was
fixed to the midrib of the larger and taller cotyledon (which enfolds the
other and smaller one, whilst still within the seed), and a mark being
placed close behind, the movement of the whole plant, that is, of the
hypocotyl and cotyledon, was traced greatly magnified on a vertical glass.
At first the plant bent so much towards the light that it was useless to
attempt to trace the movement; but at 10 A.M. heliotropism almost wholly
ceased and the first dot was

Fig. 6. Brassica oleracea: conjoint circumnutation of the hypocotyl and
cotyledons during 10 hours 45 minutes. Figure here reduced to one-half
original scale.

made on the glass. The last was made at 8.45 P.M.; seventeen dots being
altogether made in this interval of 10 h. 45 m. (see Fig. 6). It should be
noticed that when I looked shortly after 4 P.M. the bead was pointing off
the glass, but it came on again at 5.30 P.M., and the course during this
interval of 1 h. 30 m. has been filled up by imagination, but cannot be far
from correct. The bead moved seven times from side to side, and thus
described 3 ½ ellipses in 10 3/4 h.; each being completed on an average in
3 h. 4 m.

On the previous day another seedling had been observed under similar
conditions, excepting that the plant was so
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placed that a line joining the two cotyledons pointed towards the window;