bil 
49 
‘circulation, with the movement of rotation in the lower 
plants. In his Memoir he had made known two sorts of 
circulation quite distinct from each other; the one existing 
in homorganic plants, that is, in plants composed exclusively 
ofa homogeneous cellular tissue, of which each cell represents 
and contains the whole vital actions of the plant: a circulation 
which, on account of the separate gyrating motion in each 
cell, he had called rotatim ; the other peculiar to heterorganic 
plants, namely, to those provided with a double system of 
vessels united by a cellular system, in which reside exclu- 
sively the functions of formation : this last circulation is that 
to which he had confined the name cyclosis, because of the 
currents of fluid enclosed in vessels ramifying in a reticu- 
lated manner, so: as to form circles linked to each other and 
cohering by anastomoses. 
Both Brown and Amici, without attending to cyclosis, 
have published some interesting observations upon the motion 
of the juice in the cellular hairs of several heterorganic plants, 
(provided with laticiferous vessels) ; and Slack, in repeating 
the observations of Brown upon the hairs of Tradescantia 
virginica, established for the first time, in a positive manner, 
a comparison between this circulation in the hairs and the 
rotation in homorganic plants. Mr. Slack correctly observed 
that these hairs are not cellules composed of a simple mem- 
brane, but that they consist of a double tissue, the one exte- 
rior, the other interior, and that the circulation takes place 
between their two membranes. He also noticed that this 
motion in hairs does not merely consist of two currents re- 
turning upon themselves, but rather of numerous canals 
united by reticulating anastomoses. Mr. Slack therefore 
described a case of true cyclosis, but he was unacquainted 
with the nature and the different degrees of developement 
of the laticiferous system. 
More recently these observations have been repeated by 
Meyen, but although one should have expected that an ob- 
server acquainted with the real nature of cyclosis, would, at 
the first glance, have distinguished that kind of circulation 
from rotation; Meyen, on the contrary, adopts the idea of 
Slack, and even pushes his false us coge still further, by 
attempting to refute tlie unquestionable accuracy of the ob- 
servations made by the latter Botanist, when he stated that 
the circulation does not take place in the interior of a cell, 
