PHYTOGENESINS. 247 
given rise to the conflicting views of authors. But the same 
also occurs in all cells under certain circumstances, and the 
influence of the spiral fibre remains meanwhile altogether ob- 
scure and unexplained. Perhaps the foregoing may render it 
probable that the spiral is everywhere only a secondary varia- 
tion of form in the product of the vital power (the fibrin) pro- 
duced by a different tendency of the vital activity of the cell, 
so soon as this is compelled, as a certain stage of its develop- 
ment, to give up its independent individuality, and enter as an 
integral portion into the complex of the entire plant. 
I also think that we may venture, in conclusion, to deduce 
from the data above enumerated, that this indication of a spiral 
formation is the surest sign that we have no longer anything 
to do with the simple cell-membrane. 
I now return, after this somewhat lengthy digression, to my 
subject. The process of cell-formation, which I have just 
endeavoured to describe in detail, is that which I have observed 
in most of the plants which I have investigated. There are, 
however, some modifications of this process which make the 
observation of many parts very difficult, and sometimes indeed 
render it impossible, although, notwithstanding this, the law 
remains undisturbed and universally valid, because analogy 
requires it, and we can fully explain the causes of the impossi- — 
bility of direct observation. 
The difficulties which I now notice depend especially upon 
the physical and chemical properties of the substance which 
precedes the formation of cells. The materials enumerated 
above are to be regarded as scarcely anything more than sepa- 
rate facts, which, for the purpose of giving a general view and 
rendering the classification more easy, I have intentionally 
selected from the organic chemical processes of vegetable life, 
which are constantly in operation, and with which we are as 
yet totally unacquainted. Almost all these materials con- 
stantly exist together in the living plant, and it is merely 
their preponderance in a greater or lesser degree which enables 
us to say that the cell contains amylum or gum, and so forth. 
Only towards the termination of the individual life of the 
cells do we find them filled with a less number of different 
substances ; the cells which contain ethereal oil are probably 
the only instances in which we find but a single one. 
