CELL-FORMATION.

Ill

with mucilage. When the cell expands more, it becomeshollow in the interior. The mucilage remains on the wallas a thin layer, and forms a coating over the whole inter-nal surface. This is the mucilaginous layer which I havedescribed in the Algae, * and which Mold j- has named the“primordial utricle regarding it as a structure properto all cells. The mucilaginous layer is usually thicker atthe place where the nucleus of the cell lies, than over therest of the wall. Not unfrequently the nucleus lieswholly imbedded in the mucilaginous layer. Schleiden thought that it was inclosed in a duplicature of the cell-wall. But this is certainly incorrect, and is best refutedby the fact, that the nucleus may become detached, withthe mucilaginous layer, from the membrane of the cell.

Mohl conjectures that the first thing formed around anucleus is the primordial utricle, and that the membranedoes not originate until after this. The statements inregard to this are, however, too vague, and made withoutconsideration of cell-formation in the embryo-sac, so thatno minute discussion is necessary for the criticism of thephenomena in question. I merely remark that I see theorigin of the mucilaginous layer (primordial utricle) onthe internal surface of the cell in the endosperm-cells, inthe same manner as in all other cells where new contentsare formed. The mucilage at first fills the whole cavityof the cell, and subsequently merely lines the walls as athin layer. The mucilaginous layer is, therefore, asecondary phenomena in the origin of the cell-contents.

c. Of free cell-formation as a general law.

Now that I have separately brought forward the factswhich are at my command respecting free cell-formation,I will briefly collect and compare them, in order to

* See Part I of this Essay. Pay Translation, p. 268.f Botan. Zeit. 1844. (Translation in Taylor’s Scientific Memoirs, vol. iv,p. 91.)