[ 153 ] 

 XXI. Intelligence and Miscellaneous Articles. 



CAUSE OF THE CIRCULATION OF THE CHARA. 



M DONNE states that he thinks he has discovered the cause 

 • of circulation in plants, of which the Chara is a remarkable 

 example. Contrary to the opinion of several authors who have attri- 

 buted this circulation to physical agents, M. Donne supposed that its 

 cause might be found in an organic disposition, and with this view 

 entered into an examination, the result of which he thus states : — 



" After having carefully taken off the outer coating of a tube of 

 Chara hispida, and deprived it of the carbonate of lime, which inter- 

 feres with its transparency, I submit it under the microscope to a 

 methodical and graduated pressure, by the aid of M. Purkinje's 

 press. This pressure immediately detaches a great number of 

 granules. Little strings, formed of 5, 6, or more granules, are then 

 seen to put themselves in motion, turn round, and then stop if they 

 are not carried away by the current of the fluid ; other granules are 

 completely detached from one another, and free from all adhesion ; 

 amongst these are seen some which have a rotary movement, more 

 or less rapid, independent of the movement of general circulation ; 

 some turn round on themselves without changing place ; others are 

 carried along by the current, but still preserving their spontaneous 

 rotary movement. 



" These small bodies are therefore endowed with a peculiar power, 

 which they obey when they are free, but which react on the liquid 

 in which they are immersed when they are fixed. 



" The rotary motion I speak of, is independent of that of the 

 liquid in circulation ; it is often very rapid indeed in comparison 

 with the motion of circulation, and takes place when the circulation 

 is slowest or has even ceased : it is not a rare case to see two gra- 

 nules near one another moving in a contrary direction ; the follow- 

 ing experiment will show this fact in a decisive manner, 



" By pressing out the sap from a tube of Chara upon a piece of 

 glass, and submitting this drop of liquid to inspection under the 

 microscope, it is found to be composed, not only of the fluid and 

 of white particles which were in circulation, but of a certain quan- 

 tity of green granules, which the pressure has detached from the 

 sides of the tube ; the greater number of these granules are strung 

 together, and no motion is to be discovered in them, nor in the free 

 isolated granules spread over the surface of the glass. This is not 

 the case with the large oily or albuminous drops which the interior 

 fluid of the Chara forms upon difiusing itself : it is seldom that in 

 some of these drops, the transparency of which is unfortunately 

 troubled by a number of small grains, one or several green granules 

 are not found endowed with the same spontaneous rotary motion 

 which takes place in the interior of the tube itself ; these granules 

 being in their natural fluid have preserved all their properties, whilst 

 the others may be considered as dead. 



