50 



but in the space between a double tissue. Most assuredly 

 this refutation is altogether hypothetical. M. Meyen justly 

 observed that it is impossible for a true rotation to occur in 

 cavities enclosed within a double tissue ; but instead of ad- 

 mitting the reticulated currents between such tissue to be 

 referable to cyclosis, he preferred asserting that the observa- 

 tions of Brown and Slack are erroneous, although nothing 

 can be more correct that their observations, their conclusions 

 alone being false. 



If we adopt the opinion of M. Meyen, we must allow that 

 heterorganic plants, provided with a laticiferous system, have 

 two sorts of circulation in the same individual, viz. cyclosis 

 and rotation ; without understanding what relation or con- 

 nection there can be, either between the two circulations 

 themselves, or between the two circulations and the system 

 of spiral vessels. Such contradictions are inexplicable except 

 upon the supposition that M. Meyen is unacquainted with 

 the different forms, situation, extent, and the degrees of de- 

 velopement of laticiferous tissue ; especially that of the capil- 

 lary form, the sides of which are often not discernible in the 

 midst of the cellular tissue, on account of their extreme 

 tenuity and glassy transparency ; and it is this circumstance 

 that has so often prevented observers admitting, in a general 

 manner, the existence of vessels for the conveyance of latex. 



The author then proceeded to offer some observations 

 upon two cases of cyclosis, of which drawings accompanied 

 his paper. The first was Commelina coelestis ; of this a live 

 stem was represented cut through the middle of a vascular 

 bundle longitudinally. By the side of the spiral vessels a 

 focus of cyclosis was indicated ; this focus consisted of a 

 bundle of laticiferous vessels, very delicate and filamentous, 

 united together compactly in the form of a network with 

 very long meshes, in which were seen currents of latex 

 ascending and descending. Moreover, at the side of the 

 focus, in the midst of the cellular tissue, the cyclosis was 

 shewn in distinct currents, and the same thing was visible 

 between the cells of a hair. The currents of latex, separated 

 either in the cellular tissue of the stem, or in the hairs, were 

 not separated in each cell, nor isolated in the cellular mass, 

 but connected with the focus of circulation at certain points, 

 so that all the latex circulating in the cellular tissue and 

 hairs took its origin in the focus of cyclosis. 



