Dr. Burdon Sanderson read at the last meeting of the
Royal Society an interesting paper on the electrical excitation of the fly-catching plant, the Dioncea muscipula. He showed that 'the effect produced on the contractile hairs by touches is cumula- tive. The first half-dozen touches (given at intervals of two minutes each) produced no motion ; then contraction was pro- duced, but at first only after an interval of 7 seconds, then after the shorter interval of 5 seconds, and at the and of 31 touches (from the beginning) at an interval of 3 seconds. The 'next touch took effect sooner, and at the 33rd the leaf closed. At each touch after closing, the contraction -became tighter, as was proved by testing the strength of the contraction with a one- gramme weight,. It was found that the leaf only is liable to elec- trical excitation, and after one area in the leaf was exhausted and no longer affected the magnetic needle, another part of the area would do so, so that each cell in the tissue is apparently an independent centre of electrical excitability.
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