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 celestis; 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 eyclosis 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. 
"s 
