248 CONTRIBUTIONS TO 



If we now assume a cell to be completely filled with a 

 transparent solution of sugar in which there is rapidly gene- 

 rated just so much gum, as may form, by an equally quick 

 conversion into jelly, a delicate cell-membrane, the exist- 

 ence of which we cannot possibly recognise with the micro- 

 scope, in consequence of the similar refracting power of the 

 wall, the contents, and the surrounding medium ; it then be- 

 comes exceedingly probable that a number of such formative 

 processes may go on which escape our observation, and become 

 known to us only in their results, when, after the absorption 

 of the parent-cell, we suddenly find two new ones in its place. 

 If, on the other hand, our attention has been previously directed 

 to this process, we have, in the application of reagents, espe- 

 cially iodine, which is quite indispensable to the physiological 

 botanist, several means of rendering it visible in instances 

 where it is suspected to be going forward. Gradual transition 

 to the completely invisible processes are readily found by more 

 extended investigation ; I will just mention one of the most 

 difficult instances which I have met with, by way of example. 

 It occurs in the germination of the sporules of Marchantia poly- 

 morpha. Only a few, generally only from two to four of the 

 cell-nuclei which appear in the sporules, serve for the formation 

 of cells.; the others become quickly enveloped with chlorophyll, 

 and are thus withdrawn from the vital process. The transparent 

 fluid, however, in which these cytoblasts float, passes through 

 the remaining stages of the metamorphosis into cell-membrane 

 only just at the boundary of the latter, and with such rapidity 

 that the exceedingly delicate young cells cannot be distin- 

 guished by anything else than a minute, generally more or less 

 uninterrupted circle of infinitely small, black granules, and by 

 a scarcely perceptible greater transparenc} 7 of the contents of 

 the newly-formed cells in comparison with that of the parent- 

 cell, and finally, under the most favorable circumstances, by the 

 spot at which the newly-developed cells come into contact, the 

 point of juncture being still covered by the membrane of the 

 parent-cell. (PI. I, figs. 18-20.) This may perhaps be general 

 in the Cryptogamia, and especially in water plants, and probably 

 Mohl's division of the cells of Conferva may be thus explained. 



If we consider, however, that there are undoubtedly many 

 plants, among which the Fungi and infusorial Algcz should pro- 



