100

VEGETABLE CELLS.

reorganization of the solid structures, such as chlorophylland starch), which must necessarily be connected with it.But that hypothesis is placed beyond all doubt by thefollowing fact. It is well known that the union of twocells, and the mixture of their contents, do not alwaystake place. Sometimes a cell produces a germ-cell fromits own contents, when it either forms no conjugativebranch, or when this does not meet with another withwhich it can become united. In the latter case the con-tents separate from the interior of the wall, and movetoward the blind prolongation. Arrived there, any fur-ther advance being prevented, they become transformedinto a cell, and indeed exactly of the form which theypossess at this time: this happens in Zygnema stdlinum(pi. II, fig. 4). Sometimes it happens that two cells com-municate by a connecting tube, but the contents of thetwo cells do not become united. Then two germ-cellsoriginate, one of which is ellipsoidal or globular, whilethe other exhibits the form possessed by the contents,which had already begun to move before they came to astate of rest and cell-formation (pi. II, fig. 6, in Zygnemastellinum ). In both the cases here described, it mustinevitably be assumed that the membrane originates onthe surface of the contents. If these cells were formedof minute size in the interior, they must, in their ulteriordevelopment, retain their original globular or ellipsoidalshape, like all cells which originate and become developedin a free condition.

Schleiden * is inclined to attribute a different mode oforigin to the germ-cells of Spirogyra , as he says •. “ Inthe already irregularly agglomerated cell-contents, Ialmost always found a delicate cell, which I cannot butregard as the true spore, around which the green andgranular mass is merely applied, forming a false mem-brane around it, or which gradually absorbs this massinto its interior. Perhaps the.Cytoblast.

* Grundzuge der wiss. Botanik, ii, p. 31 (first edition).