110 VEGETABLE CELLS. 



I will here mention another phenomenon which I ob- 

 served a few times. I do not think that Schleiden has 

 allowed himself to be deceived by this ; yet others, who 

 may also observe it, may easily suppose it to be the process 

 of cell-formation as described by Schleiden, to which it 

 bears great resemblance. Nuclei which have attained a 

 considerable size, absorb water by endosmose. The 

 membrane of the nucleus detaches itself on one side from 

 the contents, the interspace becoming filled with water. 

 The comparison with a watch-glass is here not inapt. In 

 some cases, the membrane continues to expand, suddenly 

 bursts, and disappears. In others, this expansion goes 

 on to a variable extent, and ceases when the force of the 

 endosmose and the elasticity of the membrane come into 

 equilibrium. The membrane remains visible and is not 

 dissolved. (See fig. 9, i, k, I, m ; in h, i, k the same nu- 

 cleus is represented previous to the action of the water, 

 and in two stages after the operation of endosmose has 

 begun.) 



If the nuclei contain only one nucleolus, one may 

 readily suppose them to be cells, and the hollow space 

 round the nucleolus to be the nuclear vesicle (fig. 9, i, fc). 

 Those forms, with two or three nucleoli (fig. 9, /), how- 

 ever, prove that it is inside the nuclei that the hollow 

 spaces have been formed through the action of water, as 

 is the case in the nucleus represented in fig. 9, c-g. The 

 contents of the nucleus are pretty sharply defined where 

 they join the water. The outer circumference of the 

 nucleus exhibits a dark line, which is formed by the de- 

 licate membrane lying close upon the contents, and which, 

 therefore, is lost when this membrane has become detached 

 from the contents (fig. 9, h, /, 0). These facts furnish a 

 new proof that the nuclei possess a membrane and are 

 vesicles. 



The young cell appears at first as a layer of mucilage 

 surrounding the nucleus. Subsequently a membrane 

 becomes visible on the surface of the mucilage. Conse- 

 quently the cell is at first, besides the nucleus, quite filled 



