CELL FORMATION BY UNION. 49 



B. FORMATION OF VEGETATIVE CELLS. 



1. By the progressive formation of a division wall. 



2. 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. 



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

 ple classification, as follows : 



A. FREE CELL-FORMATION. 



1. Intracellular. 



2. Extracellular [Rejuvenescence]. 



B. FORMATION OF CELLS BY DIVISION. 



1. Progressive division. 



2. Simultaneous division. 



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

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

 that the nuclei of the cells which coalesce to form the plaemodium 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." (8. H. Vines in Apn. to Sachs' Text-Book of Botany. 

 Second English Edition, p. 945.) 



