ELEJIEKTARY STRUCTURE. 



57 



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 

 utricle and the nucleus has been 

 already spoken of in treating of 

 those bodies (see p. 7 et seq.). This 

 process of cell-formation is some- 

 what diiferently described by 

 Henfrey thus: "The new cell is 

 formed by a portion of the parent 

 primordial utricle separating itself 

 from the rest of the protoplasm, as- 

 suming a globular or oval form, 

 and secreting a cellulose mem- 

 brane upon its surface, so as to 

 form a new cell, lying free in the 

 cavity of the parent primordial 

 utricle." The antecedent forma- 

 tion of a nucleus is not here al- 

 luded to, except the separated 

 portion of the primordial utricle 

 is to be regarded as such; alto- 

 gether Henfrey appears to consi- 

 der the nucleus as by no means an 



Fig. 140. 



Fig. 139. 



t\y. i;i!<. Cells tium the embryo-sac 

 of Chumadoreu Schieckitna in the 

 act of formation, a. Tlie youngest 

 part, consisting of nuclei and pro- 

 toplasm, b. Newly formed cells, 

 c, d. Cells still further developed, 

 M'ith nuclei adhering to their sides. 

 After Schleiden. 



Fig. 140. 2. The part of /i;;. 139, 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 by pressure. 8. The cells of ^j;. 139, d, in a higher degree of develop- 

 ment, the cell-walls having already united. After Schleiden. 



