CHAPTER II. 



OF GEOWTH IN THE VEGETAL KINGDOM. 



Cellular proliferation is far from being accomplished in a uniform 

 manner. It results from various processes, which sometimes 

 even are more or less combined, but of which the principal 

 may be arranged under the following heads — 1, simple division or 

 segmentation, scission; 2, budding, germination or surculation ; 3, 

 copulation or conjugation ; 4, endogenous generation. 



In cellular segmentation it is first of all the azotized utricule, 

 the inner envelope of the cellular protoplasm, which depresses 

 itself, narrows itself into a circular furrow. Afterwards, the 

 external tunic in cellulose places itself in its turn in the depres- 

 sion, which, becoming deeper and deeper, at last forms a 

 partition at first incomplete and pierced with a circular hole, 

 afterwards complete. While this division is taking place, a 

 second nucleus appears in tha,t one of the two cavities which was 

 primitively destitute of it. The result of this very simple evolu- 

 tion is the formation of a new cell, which divides itself in its 

 turn. M. Mohl was the first to observe closely this cellular 

 unfolding in the terminal cell of the confervBe. It has since 

 been affirmed regarding most of the vegetal tissues. It is thus 

 that the ligneous cell of the phanerogams form their layers and 

 their fibrous bundles ; it is thus that the cells multiply themselves 

 in the sporangia, and the spores of the algae, &c., &c. Sometimes, 

 as in the cells of the pith of the dicotyledons, the division of the 

 nucleus precedes that of the cell. 



