42 Dr. M. J. Schleiden’s Observations on 
tion ; but instead of observing their development into rings, 
many have only inferred that the annular vessels were of far 
later origin. Moreover, the formation usually proceeds, at 
the moment when the bud comes to development, so rapidly, 
that the observation of the intermediate stages is rendered 
almost impossible by it. For obtaining a successful result 
everything here depends on finding a plant in which all these 
difficulties exist in a slighter degree, and on which therefore 
the process may be accurately observed ; if once a clear in- 
sight has been acquired in this way, it is easy to find oneself 
at home, even with the more difficult plants. I found for these 
inquiries the Campelia Zanonia, Rich. (frequent in most hot- 
houses), and the subterranean stem of Equisetum arvense most 
advantageous. 
If the very youngest internodes of the buds of the first- 
mentioned plant be examined, a single extremely delicate and 
densely-wound spiral vessel is found in all the as yet scarcely 
limited vascular bundles. In older internodes the convo- 
lutions of this vessel are found further distant from one an- 
other, and near it exteriorly a new-formed narrow-threaded 
spiral vessel. But if we consider in this period the first 
formed vessel more accurately, Plate (fig. 11.), it will be seen 
that all convolutions are not separated in the same manner from 
one another, but that almost in regular alternation two en- 
tire coils adhere firmly together, and one convolution is drawn 
out. In still older mternodes the extension is found to be 
so far advanced, that the free coil loosened from the cellular 
membrane frequently reaches as a mere band with a steep 
ascent from the one ring formed of two closed convolutions to 
the other. On still further developed vessels this elongated 
coil is seen corroded by the reabsorbing action of the cell, and 
all the stages of transition, as they are represented in the 
Plate (from fig. 1 to 5,) are frequently found in the continuity 
of a single vessel. Lastly, on still older vessels, the connect- 
ing coil is already perfectly dissolved; but there may still be 
observed on the isolated rings the extremities of the previous 
spiral fibre (fig. 6, 7, a.). Even on highly developed vessels, 
we still find on the perfectly closed and smoothened rings, 
their composition of two coils now and then indicated by 
single delicate dark lines (fig. 8—10.). Exactly the same 
process may likewise be easily followed in the subterranean 
stems of Eguisetum arvense; and in particular we frequently 
find long streaks in vessels modified as is represented in fig. 11. 
as the first stage of transition to the formation of rings. 
I must still mention another point respecting which I do 
not at present agree with M. Mohl; it relates to the succes- 
