316 DION^A MUSCIPULA. Chap. XIII. 



is transmitted in like manner in all directions tlirough 

 the cellular tissue ; but that its rate is largely governed 

 by the length of the cells and the direction of their 

 longer axes. Thin sections of a leaf of Dionaea were 

 made by my son, and the cells, both those of the 

 central and of the more superficial layers, were found 

 much elongated, with their longer axes directed to- 

 wards the midrib ; and it is in this direction that the 

 motor impulse must be sent with great rapidity from 

 one lobe to the other, as both close simultaneously. 

 The central parenchymatous cells are larger, more 

 loosely attached together, and have more delicate walls 

 than the more superficial cells. A thick mass of cel- 

 lular tissue forms the upper surface of the midrib 

 over the great central bundle of vessels. 



When the filaments were roughly touched, at the 

 bases of which slits had been made, either on both 

 sides or on one side, parallel to the midrib or at right 

 angles to it, the two lobes, or only one, moved. In 

 one of these cases, the lobe on the side which bore the 

 filament that was tonched moved, but in three other 

 cases the opposite lobe alone moved ; so that an injury 

 which was sufficient to prevent a lobe moving did not 

 prevent the transmission from it of a stimulus which 

 excited the opposite lobe to move. We thus also 

 learn that, although normally both lobes move to- 

 gether, each has the power of independent movement. 

 A case, indeed, has already been given of a torpid 

 leaf that had lately re-opened after catching an 

 insect, of which one lobe alone moved when irritated. 

 Moreover, one end of the same lobe can close and re- 

 expand, independently of the other end, as was seen 

 in some of the foregoing experiments. 



When the lobes, which are rather thick, close, no trace 

 of wrinkling can bo seen on any part of their upper 



