CELL FORMATION BY UNION. 49 



B. — Formation of Vegetative Cells. 



1. By the progressive formation of a division wall. 

 3. By the simultaneous formation of a division wall. 

 The main objection to this classification is that its principal divis- 

 ions are based upon physiological distinctions alone. 



(J) Duchartre, in his "Elements de Botanique," makes a very sim- 

 ple classification, as follows : 



A. — Febe Cell-Fokmation. 



1. Intracellular. 



2. Extracellular [Rejuvenescence]. 



B. — Fobmatiok av Cells by Division. 

 1. Progressive division. * 



8. Simultaneous division. 



Note on Paragraph 56. " From the researches of Schmitz on the 

 Myxomycetes (Sitzber. d. nieder-rhein. Ges. in Bonn, 1879), it appears 

 that the nuclei of the cells which coalesce to form tlie plasmodium do 

 not fuse, but remain distinct : this case of coalescence of cells cannot, 

 therefore, be any longer regarded as an instance of cell-formation by 

 conjugation." (S. H. Vines in App. to Sachs' I'ext-Book of Botany. 

 Second English Edition, p. 945.) 



