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THE POPULAR SCIENCE MONTHLY. 



occurs in the leaves of some other leguminous plants, in several species 

 of Oxalls, etc. M. Bert has observed that the sensitiveness is de- 

 stroyed by the continual application of chloroform, and also by placing 

 the plant constantly in the dark or in green light. 



Similar movements to that of the Sensitive-plant, but occurring 

 spontaneously, may be observed in other plants. Thus in the Des- 

 modlum gyrans or " Telegraph-plant," sometimes grown in our hot- 

 houses, belonging to the same order, Leguminosa?, the leaf consists of 

 three leaflets, a large central, and two smaller side ones. The motion 

 is especially observable in the small side-leaflets, which on a warm 

 summer's clay may be seen to rise and fall by a succession of jerking 

 movements ; now stopping for some time, then moving briskly, always 

 resting for a while in some part of their course, and starting again 

 without apparent cause, " seemingly of their own will," as Prof. Asa 

 Gray remarks. The movement is not simply up and down, but the 

 end of the moving leaflet sweeps more or less of a circuit. It is not 

 set in motion by a touch, but begins, goes on, and stops, of itself. 



An exceedingly remarkable instance of sensitiveness occurs in the 

 case of the " Venus's Fly-trap " of North Carolina (Dionwa mitscipula), 



Fig. 7. 



represented in Fig. 7. The mid-rib of each leaf serves as a kind of 

 hino-e. When the inside of the blade of the leaf, or the fine bristles 

 which grow on its surface, are touched by any foreign substance, the 

 hinge suddenly closes, and if the intruding substance be a fly or other 

 small object, it is immediately imprisoned as represented in the figure, 

 the teeth on the margin of the leaf closing firmly upon one another 

 like a steel trap, the sides of the trap then flatten down and press firmly 



