PHYTOGENESIS. 247 



given rise to the conflicting views of authors. Hut the Bame 

 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 coll, 

 so soon as this is compelled, as a certain stage of its develop- 

 ment, to give up its independent individuality, and enter ;is 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 ju-1 

 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 sav that the cell contains ainvlinn or gum, and BO forth, 

 Onlv towards the termination of the individual life of tin- 

 cells do we find them filled with a le^s number of different 

 substances; the cells which contain ethereal oil are probably 

 the onlv instances in which we find but a Bingle one. 



