CELL-FORMATION.

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is mostly somewhat more dense than the substance of thenucleus; sometimes it is brighter than the latter.

The mucilage surrounding the nucleus now continuallyincreases in quantity; the nucleus is alioays distinctlyvisible, situated at the periphery (fig. 8,/). There are,however, isolated exceptional cases here, where the nucleusis free, and more or less removed from the circumference.

The mucilage then becomes evidently granular, and adistinct membrane is to be made out upon its surface(fig. 8 ,g). The latter frequently becomes visible even whenthe contents are still homogeneous. In this stage, as inthe preceding, the nucleus is mostly less dense than thesurrounding mucilage, and therefore appears like a clearerspace. The cell is now visibly formed. Whether themembrane first originates at the time it becomes visible,or had originated at a still earlier period, can scarcely beascertained by observation. The latter appears to meprobable.

According to Schleiden , the cell-membrane originatesimmediately on the surface of the nucleus; it absorbswatery fluid by endosmose, and expands ; the nucleus re-mains attached on one side of the cell; the cell is a fine,transparent vesicle ; its contents a watery fluid, and ap-pear merely as a hollow space between the nucleus andthe granular mucilage of the embryo-sac, which is pushedbackward by its expansion.* Sclileiden adds, that thecells become wholly dissolved in a few minutes in distilledwater, so that only the nuclei remain. I confess that Ihave never seen such very clear and transparent cells.In most cases I find the contents of the cells more denseand darker than those of the nucleus ; rarely clearer, buteven then always either homogeneously mucilaginous orfinely granular. In like manner, I did indeed see variouseffects on the young cells and their contents produced bythe action of w T ater, but never a solution.

* Muller’s Archiv , 1838. [Schleiden has changed this opinion in thelatest edition of his ‘ Principles of Botany’ 1849). See Appendix to Dr.Lankester’s Translation.—A. It.]