142 VEGETABLE CELLS. 



nucleus before its growth begins, and retains it subse- 

 quently. A free nucleus also exists afterwards in the 

 prolonged portion, and this probably originates sponta- 

 neously and independently of the primary nucleus of the 

 original cell. Each of the two secondary-cells possesses 

 a central nucleus. This branching cell-formation holds 

 good for those plants in which the formation of cellular 

 tissue follows the rule described under 2. 



B. The expanding cell originally possesses a lateral 

 (primary) nucleus. A second nucleus is subsequently 

 found in the prolonged portion, probably originating 

 spontaneously and independently of the primary nucleus. 

 Each of the two secondary-cells possesses a lateral nucleus. 

 This branching cell-formation occurs in such plants as 

 have their cellular tissue formed according to the rule 

 given under 3. 



9. A cell grows out into a branch. The whole of the 

 contents of the branch (Jf it be short), or the terminal por- 

 tion of its contents (when the branch is long), becomes 

 isolated, and, by the formation of a membrane over its 

 whole surface, is converted into a cell, which corresponds 

 exactly to the cavity of the very short branch, or to the 

 whole of the end of a longer branch. In this way the 

 germ-cells of several Algse (e. g. Vaucheria) and Fungi 

 are formed. The behaviour of the nucleus is not yet 

 sufficiently known. The parent-cell possesses a lateral or 

 central nucleus ; the secondary cell likewise. The nu- 

 cleus of the secondary cell probably originates in the 

 branch, spontaneously and independently of the (primary) 

 nucleus of the parent-cell. This mode of cell-formation 

 is closely allied to that mentioned under 8. But there 

 the division always occurs by means of a septum, which, 

 as soon as it is thick enough, appears to be formed of 

 two layers of equal thickness. From this condition of 

 the wall we may conclude that two cells are simulta- 

 neously formed, dividing in the contents and cavity of 

 the parent-cell. Here, on the other hand, only one la- 

 mella can be perceived in the curved septum, which 



