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 homorcjanic plants, that is, in plants composed exclusively 

 of a 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 I'otatim ; 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 wiiich 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 linlvcd 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 horn organic 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 iheir 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 comparison still further, by 

 attempting to refute the 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, 



