33 



" Electricity does not, as might have been anticipated, pro- 

 duce any decided change in the circulation in the acpiatic 

 plants. A weak cm-rent produces literally no effect ; if it is 

 increased in intensity a temporary stagnation ensues, but the 

 motion soon begins again, and continues in spite of the cur- 

 rent ; by again exalting the intensity of the electrical force, the 

 same effect is produced; wliich leads one to bebeve that it acts 

 precisely in the same way as any mechanical injury would do. 



"The effect of direct violence to the valisneria is by 

 no means uniform : at one time pressure will destroy all 

 circulation entirely ; at another, the same amount will pro- 

 duce stagnation only while it is kept up; at another, the 

 pressure must go on to complete disintegration of the leaf 

 before any change is noticed. An experiment illustrated the 

 same fact : two slips were cut from the same leaf, and circu- 

 lation was steady in each ; both were scraped with a penknife 

 until one side of the leaf was denuded of its epidermis ; in 

 one the circulation was as vigorous as ever, while in the other 

 it had ceased entirely, and was not re-estabbshed till fifteen 

 minutes had elapsed. 



" The chara is much more sensible of mechanical violence 

 than the vabsneria. 



"Actual injury to a cell, such as rupture of its wall, causes 

 complete cessation of circulation in that individual. 



" There are, however, two statements made by Meyen that 

 the author could not account for, except from the fact he has 

 before mentioned respecting the uncertain and contradictory 

 results obtained from the same experiments at different times. 

 This distinguished botanist states, ( that if we cut off a single 

 branch of a chara, the motion ceases for a long time in the 

 adjacent cells/ 'In vabsneria, indeed/ he adds, 'this fre- 

 quently lasts for ten or twelve minutes, until the motion in 

 the cells of the prepared section again recommences with perfect 

 activity/ Now, so far is this from correct, according to 

 the author's experience, that he would have recorded the direct 



