OF THE ELEMENTARY STEUCTL'RES. 



731 



cell-formation oceurriug in plants. 

 Subsequently he modified his view.'^ 

 materially, not only as regarded 

 the manner in which it took place, 

 but also as to its universality, and 

 he now admits that it is only one 

 principal mode of cell-formation. 

 The manner in which he describes 

 it as taking place is as follows {figs. 

 1099 and 1100):— a portion of the 

 protoplasm collects into a more or 

 less rounded or somewhat oval form, 

 with a defined outer border, thus 

 forming the nucleus of the cell : 

 upon this a layer of protoplasm is 

 deposited, which assumes the form 

 of a membrane, and expands so as 

 to form a vesicle ; on the outside ol 

 this a cellulose membrane is se- 

 creted, and the formation of the 

 cell is completed. The proto- 

 plasmic vesicle in this case forms 

 the subsequent lining of the young 

 cells, and constitutes the " primor- 

 dial utricle " of Mohl. The ulti- 

 mate destination of the primordial 



Fig. 1099. 



Fig. 1099. Cells from the eiiil)r>"i)-sac 

 (if Chamcedorea Schiedeana In the 

 act of formation, a. The youngest 

 part,, consisting of nuclei and pro- 

 toplasm, h. Newly formed cells. 

 c, d. Cells ftill funher developed, 

 with nuclei adhering to their side.-. 

 After Schleideu. 



1100. 



Fio.wm. •>. The pan i^t ji,i. 1099, a, more highly magnified. 3. A nucleus 

 still more highly magnified. 4. A nucleus with the cell forming upon 

 it. 5. The same more highly magnified. 6. The same: the nucleus 

 here shows two nucleoli. 7. The nucleus of 6, after the destruction of 

 the cell hy pressure. 8. The cells of fig. J099, d, in a higher desree of 

 development, the cell-walls having already united. After Schleideu. 



