“Development, and Structure of the Vegetable Cell. 85 
prove by their development (De Cella vital, 1843, pp. 80-84 ; 
Bot. Zeit. 1843, p. 457, and 1849, p. 3861), and have here de- 
monstrated, I think, as regards those occurring in the Conferve. 
The evident function of these cells, which are constantly 
engaged in a brisk exchange of materials and in rapid develop- 
ment, is the conversion into new and higher organic com- 
pounds, both of the material secreted inwards by the assimi- 
lating membrane of the tissue-cells to which they belong, and of 
that mechanically admitted from the surrounding medium by 
this imbibitory and diosmotic membrane. In favour of this 
supposition is the- fact that the different vesicles which are 
enclosed within a single cell contain very diverse materials, 
usually all quite different from the fluid contents of the cell. 
I have already called attention to this circumstance in my 
memoir ‘ De Cella vitali’ with reference to the development of 
those vesicles which contain colouring-matter, starch, oil, &c., 
the cellular nature of which, however, is generally recognized. 
But why should the vesicles which contain colourless matters, 
partly in aqueous solution (sugar, mucilage, dextrine?, cellu- 
line, &c.), be regarded as something different from cells? 
Their membrane has physical properties similar to those of re- 
coguized cell-membranes ; its development is the same; and it 
increases in size in the same manner, a mutual relation of its 
proper augmenting substance to its contents being recognizable. 
We are not justified in giving the name of a cell only to those 
elementary organs whose membrane in a. certain state of develops 
ment exhibits the reaction of cellulose, as indeed is proved by 
the Confervze just referred to, even if we leave out of considera- 
tion the cells of the animal organism. The idea of the cell is 
anatomical, and is to be deduced from the mode of development 
of the organization, and not from the chemical nature of the 
material of which its membrane is composed. 
The transitory cells contained in the tissue-cells undoubtedly 
serve for the elaboration of all the constituents of the cell-juice 
(their intercellular substance), which they are capable of assimi- 
lating ; and when they have fulfilled this task, they are them- 
selves in turn liquefied and used as nutriment by other neigh- 
bouring similar organizations, or even by the membrane of their 
mother cell. This product of the solution of these secretion- 
cells is also carried out from the cell by exosmose (?), and con- 
ducted, in the general nutritive fluid, which imbues the inter- 
cellular spaces, the outermost membranes in process of resorp- 
tion, and the intercellular substance of the tissue-cells which is 
produced from this, into distant parts of the organism, to serve 
there for the formation and development of new elementary 
organs. 
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