ABSTRACT
This memoir, which constitutes the first part of researches respecting the vegetable-cell, is dedicated to the author’s friend, Dr. F. Cohn. Its object is to afford a new doctrine and new views with respect to the primordial utricle, differing from those at present entertained. The author first proceeds to give an account of the primordial utricle, in accordance with which the principal part in the life of the cell is ascribed to that element which has been regarded as the essential, often the only completely closed, nitrogenous membrane of the plant-cell, and upon this subject the statements of some observers are communicated. A second section treats of the disposition of the contents of the vegetable-cell; these contents consist of the proper cell-fluid, which is always found in the interior, and of the external, peripheral, surrounding protoplasma (or more shortly, plasma), in which the granular portions of the cell-contents are always imbedded. A distinct lamination is apparent in this plasma, that is to say, it is constituted of an external, colourless layer applied to the cell-wall, and which never presents any granules, and termed by the author “the cutaneous layer,” and of an internal, frequently of a dense mucoid consistence and granular aspect, “the granular layer “of the author. When this granular layer is of some thickness the chlorophyll granules will be found lying in its outer portion, whilst the inner part will be seen to consist merely of a colourless, muco-granular substance, in which, it is true, many kinds of colourless, coarse, granular particles occur, but never chlorophyll-granules or amorphous chlorophyll. The parietal cytoblast is invariably lodged in the “granular layer,” and when this layer consists of two portions it is always found in the inner one. In cases where movement is observed in the cell, it always takes place at the boundary between the “granular layer” and the cellfluid. When the granular layer is thin, the whole of it moves together with the chlorophyll granules imbedded in it, but when it is divided into two portions, the movement involves only the inner layers beneath the chlorophyll-granules (Chara). The author supposes that the formative activity of the cell-contents is specially seated at the line of junction of the cell-fluid with the granular layer, and that it is the cause of the motion. In cases where the plasma does not constitute a continuous lining to the wall, it cannot, by means of reagents, be detached from the wall with a definite outline, but in the shape of a variously formed net-work of streaks of plasma. But when it constitutes a complete and uniform covering, it contracts in a continuous form under the action of the reagent, and under certain conditions assumes the false appearance of a membrane. Lastly, in cases where the plasma is divided, even in the cell, into two distinct layers, not only does the outer layer appear as a membrane, but the granular layer also presents a defined boundary. Whenever powerful re-agents are applied, and a rapid contraction thus induced, phenomena are always manifested, which necessarily lead to the assumption of the existence of a primordial utricle, although many different things have been included under that term. But when cells in which the primordial utricle is displayed in the most distinct form are treated with weak re-agents, although the same results are ultimately attained, the process, owing to the more gradual way in which it is effected, may be accurately observed, and it will thus be seen that it is not smooth membranes which are separated from each other, but a glutinous substance which is detached from a membrane to which it was adherent; the detachment frequently takes place only partially, and the connexion with the wall is maintained by isolated threads of plasma, which become more and more attenuated or are ruptured, until, at last, the outermost layer of the plasma, contracting, assumes the appearance of a membrane. This slow separation from the wall satisfactorily shows, in every case, that the internal coating of the cell is composed of a muco-glutinous, viscous substance, and that it is not, properly speaking, a membrane. The same considerations also confirm the author in his opinion that, when large cells are treated with slowly acting re-agents, the contents surrounded by the “cutaneous layer “often contract into two, or, more rarely, into several segments, whose connective portions becoming gradually attenuated are ultimately ruptured, and then isolated, though appearing to be bounded by an equally even and sharply-defined outline, as that of the whole contents previous to their division.
