Development, and Structure of the Vegetable Cell. 86 



prove by their development (De Cells vitali, 1843, pp. 30-84; 

 Bot. Zeit. iai3, p. 457, and 1849, p. 361), and have here de- 

 monstrated, I think, as regards those occurring in the Confervae. 



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 belonjr, and of 

 that mechanically admitted from the surrounding medium by 

 this imbibitory and dioamotic membrane. In favour of thia 

 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 alreadv 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?, oellu- 

 fine, &c.), be r^arded as something different firom cells? 

 Their membrane has physical properties similar to those of re- 

 cognized cell-membranes ; its development is the same ; and it 

 increases in size in the same manner, a matual relation of its 

 proper augmenting substance to its contents being recognisable. 



We are not justified in giving the name of a cell only to thoee 

 elementary organs whose membrane in a certain state of develop- 

 ment exhibits the reaction of cellulose, as indeed is proved by 

 the Confervae just referred to, even if we leave out of considera- 

 tion the cells of the animal organism. The idea of the cell ie 

 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 tissne-celb undoubtedly 

 serve for the elaboration of all the constituents of the cell-juice 

 {their intercellular substiince), which thty arc 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 ser>'e 

 there for the formation and development of new elementary 

 organs. 



8* 



