Another full-grown leaf had a filament attached externally along one side of the midrib and parallel to it, so that the filament would move if the lobes closed.  It should be first stated that, although a touch on one of the sensitive hairs of a vigorous leaf causes it to close quickly, often almost instantly, yet when a bit of damp meat or some solution of carbonate of ammonia is placed on the lobes, they close so slowly that generally 24 h. is required for the completion of the act.  The above leaf was first observed for 2 h. 30 m., and did not circumnutate, but it ought to have been observed for a [page 241] longer period; although, as we have seen, a young leaf completed a fairly large ellipse in 2 h.  A drop of an infusion of raw meat was then placed on the leaf, and within 2 h. the glass filament rose a little; and this implies that the lobes had begun to close, and perhaps the petiole to rise.  It continued to rise with extreme slowness for the next 8 h. 30 m.  The position of the pot was then (7.15 P.M., Sept. 24th) slightly changed and an additional drop of the infusion given, and a new tracing was begun (Fig. 107).  By 10.50 P.M. the filament had risen only a little more, and it fell during the night.  On the following morning the lobes were closing more quickly, and by 5 P.M. it was evident to the eye that they had closed considerably; by 8.48.  P.M. this was still plainer, and by 10.45 P.M. the marginal spikes were interlocked.  The leaf fell a little during the night, and next morning (25th) at 7 A.M. the lobes were completely shut.  The course pursued, as may be seen in the figure, was

Fig. 107.  Dionoea muscipula:  closure of the lobes and circumnutation of a full-grown leaf, whilst absorbing an infusion of raw meat, traced in darkness, from 7.15 P.M.  Sept. 24th to 9 A.M. 26th.  Apex of leaf 8 ½ inches from the vertical glass.  Figure here reduced to two-thirds of original scale.

strongly zigzag, and this indicates that the closing of the lobes was combined with the circumnutation of the whole leaf; and there cannot be much doubt, considering how motionless the leaf was during 2 h. 30 m. before it received the infusion, that the absorption of the animal matter had excited it to circumnutate.  The leaf was occasionally observed for the next four days, but was kept in rather too cool a place; nevertheless, it continued to circumnutate to a small extent, and the lobes remained closed.

It is sometimes stated in botanical works that the lobes close or sleep at night; but this is an error.  To test the statement, very long glass filaments were fixed inside the two lobes of three leaves, and the distances between their tips were measured in the middle of the day and at night; but no difference could be detected.