CHAP. XIII. 
CIRCULATION OF THE SAP. 
393 
but to vital force ; and, also, that the rapidity of the movement 
is increased by an elevated, and diminished by a lowered, 
temperature, the mean rate of motion of the swimming 
granules being a millimetre (rVifo ^ Vine) in 35 or 36 
seconds. 
Similar motions have been seen in several other plants. 
In the cells of Hydrocharis Morsus-Ranse the fluid has been 
observed to move round and round their sides in a rotatory 
manner, which, however, has not been seen to follow any 
particular law. 
Pouchet and Meyen (Ann, Sc.^ n. s., iv. 257.) have remarked 
it in the longer cells of the stem of Zannichellia palustris, and 
the latter in Vallisneria, Stratiotes, Potamogeton, and the 
radical hairs of Marchantia. It may be distinctly seen in 
Equisetum. According to Schultz (Arch, Bot, ii. 425.), it is 
also visible in Podostemaceae, Ceratophyllum, Naiadaceae, 
Zosteraceac, Lemna, Mosses, Hepaticae, Lichens, Algae, and 
Fungi. The rotation in Vallisneria canadensis is most beauti- 
ful. In large cylindrical cells filled with a transparent fluid, 
there float large brilliantly green spherules, which rotate up one 
side and down another with a slow motion, sometimes crowd- 
ing together, sometimes distant, and occasionally stopping. 
There is, moreover, among the woody tubes, a more rapid 
movement of very minute oval bodies, which goes on in lines 
upwards and downwards. 
According to Meyen, the granules seen moving in the 
rotating currents are of different kinds (Ann, Sc,, n. s., iv. 
261.), the larger being grains of starch, others vesicles slightly 
coloured by chlorophyll, and some being drops of oil. I 
find but little trace of faecula in Vallisneria, tincture of iodine 
chiefly producing a brown colour upon the granules, but here 
and there a blue nucleus was visible ; perhaps the result 
would have been different, had the watery infusion of iodine 
been employed. 
Of Cyclosis, 
At page 35. a particular kind of tissue, called cinenchyma, 
or vessels of the latex, has been mentioned. It is in this 
