CELL-FORMATION. 139 



cells in the special parent-cells of the Rhizocarpeae and 

 Phanerogamia. The special parent-cells contain a central 

 nucleus. This disappears, and soon afterwards we find 

 in the special-parent-cell a spore- or pollen-cell completely 

 filling it, with a (primary) lateral nucleus. How this cell 

 is formed, whether free in the contents, or around the 

 whole contents, is still unknown. 



2 . The cen tral primary nucleus of the parent-cell divides 

 into two secondary nuclei; the entire contents separate 

 into two portions, each of which has one of these nuclei 

 in its interior. The parent-cell divides by parietal cell- 

 formation into two cells ivith central nuclei. This process 

 is met with in the formation of cellular tissue in the 

 Algae (and the Lichens ?), and in the reproductive cell- 

 formation of many one-celled or several-celled genera of 

 Algae. 



3. A central nucleus appears in the parent-cell, and di- 

 vides into two secondary nuclei. The contents separate 

 into two portions, each of which includes one of these two 

 nuclei. The parent-cell divides, by parietal cell-formation, 

 into two cells with lateral nuclei. Here are to be enume- 

 rated the formation of cellular tissue of (most Fungi ?) 

 Florideae, Hepaticae, Mosses, Ferns, Lycopodiaceae, Cha- 

 raceae, Equisetaceae, Rhizocarpeae, and Phanerogamia. It 

 is still uncertain whether the central, dividing nucleus is 

 the primary nucleus of the parent-cell, becoming detached 

 from the wall, and advancing into the centre, or whether 

 it is a newly-formed nucleus, originating in the centre, 

 after the solution of the primary, lateral nucleus. The 

 settlement of this question will at once decide, whether 

 this cell-formation is actually different from that mentioned 

 under 2, or is to be considered as merely a peculiar 

 modification of it. With regard to the formation of 

 the stomates of the Phanerogamia, I have expressed the 

 opinion, that the primary nucleus of the epidermal cell 

 becomes absorbed and that a new central nucleus is 

 formed.* Mohl,f on the other hand, asserts of the same 



* Linmca, 18 2, p. 238. f Vcrmischte Scliriften, p. 258. 



