328 
PHYSIOLOGY. 
BOOK II. 
plants, when filled with fluid, there is a very general rotatory 
movement, which is confined to each particular cell. This, it 
is obvious, can form no part of the general circulation of the 
system, which must often occur with great rapidity, and which 
must take place from the roots to the extremities. The ro- 
tatory motion may perhaps be considered a sort of motion of 
digestion, and connected with the chemical changes which 
matter undergoes in the cells from the united action of light, 
heat, and air. 
Another sort of motion, which it is probable is common to 
all descriptions of plants, has been seen by Link and others, 
particularly by Schultz, in the Chelidonium, Ficus carica, and 
other plants. It is described as an exceedingly rapid motion 
of the fluid, which rushes out of one set of vessels into another, 
in a constant uninterrupted stream. This has been denied, 
it is true, by Dutrochet ; but he does not appear to have 
succeeded in seeing that which is nevertheless visible enough, 
if proper precautions are taken. Meyer, Mirbel, and Cassini 
confirm the statements of Schultz ; and to their testimony I 
may be permitted to add my own. In Alisma plantago, and 
the transparent stipules of Ficus elastica, I have distinctly seen 
powerful currents, such as are described, rushing along tubes, 
like a stream of water down an inclined channel. It is never- 
theless extremely doubtful whether this is a special move- 
ment. It is rather to be considered a part of the general 
system of circulation of the fluids, if it is not indeed a motion 
produced by the rapid emptying of wounded intercellular pas- 
sages. We must wait, however, for the appearance of the 
memoir of Schultz upon this subject, which at present is only 
known by the report upon it by a Committee of the Institute. 
The course ivhich is taken hy the sap after entering a plant, is 
the next subject of consideration. The opinion of the old 
botanists was, that it ascended from the roots between the 
bark and the wood : but this has been long disproved by 
modern investigators, and especially by the experiments of 
Knight. If a trunk is cut through in the spring, at the 
time the sap is rising, this fluid will be found to exude more 
or less from all parts of the surface of the section, except the 
hardest heart-wood, but most copiously from the alburnum. 
