100 VEGETABLE CELLS. 



reorganization of the solid structures, such as chlorophyll 

 and starch), which must necessarily be connected with it. 

 But that hypothesis is placed beyond all doubt by the 

 following fact. It is well known that the union of two 

 cells, and the mixture of their contents, do not always 

 take place. Sometimes a cell produces a germ-cell from 

 its own contents, when it either forms no conjugative 

 branch, or when this does not meet with another with 

 which it can become united. In the latter case the con- 

 tents separate from the interior of the wall, and move 

 toward the blind prolongation. Arrived there, any fur- 

 ther advance being prevented, they become transformed 

 into a cell, and indeed exactly of the form which they 

 possess 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 the 

 two cells do not become united. Then two germ-cells 

 originate, one of which is ellipsoidal or globular, while 

 the other exhibits the form possessed by the contents, 

 which had already begun to move before they came to a 

 state of rest and cell-formation (pi. II, fig. 6, in Zygnema 

 stellinum). In both the cases here described, it must 

 inevitably be assumed that the membrane originates on 

 the surface of the contents. If these cells were formed 

 of minute size in the interior, they must, in their ulterior 

 development, retain their original globular or ellipsoidal 

 shape, like all cells which originate and become developed 

 in a free condition. 



Schleiden* is inclined to attribute a different mode of 

 origin to the germ-cells of Spirogyra, as he says : "In 

 the already irregularly agglomerated cell-contents, I 

 almost always found a delicate cell, which I cannot but 

 regard as the true spore, around which the green and 

 granular mass is merely applied, forming a false mem- 

 brane around it, or which gradually absorbs this mass 

 into its interior. Perhaps the Cytoblast 



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



