REJUVENESCENCE IN NATURE. 123 



in physiological than in morphological respects; for to 

 the cell is committed all the vital activity of the plant ; 

 the material and form of the plant are produced in and 

 through it. In the cell resides the w'bnderful power of 

 preparing the organic substances, which no other chemical 

 laboratory has the means of forming ; in it the force of 

 endosmotic absorption and excretion, and that admirable 

 circulation, not yet physically explained, by which the 

 contents are, in the most varied manners, either imper- 

 ceptibly diffused, or driven in active currents ; in it the 

 force of organic production of form and of growth, and, 

 finally, the force of transformation and reconstruction, on 

 which depend the multiplication and propagation of 

 plants. The cell is, therefore, the immediate focus of 

 Rejuvenescence, the point from whence come all the 

 phenomena of Rejuvenescence in the building up of the 

 articulated (or complex) organism of the plant. Hence, 

 if we wish to become intimately acquainted with the 

 phenomenon of Rejuvenescence, we must search it out in 

 the cell itself. In the outset we distinguished two periods 

 in the process of Rejuvenescence, the period of retro- 

 gression, of solution and removal of the old, and the 

 movement of renewed progress, the repeated construction 

 and reformation ; accordingly, after a preliminary con- 

 sideration of the formation of the cell in general, we shall 

 examine the phenomena of Rejuvenescence in the life of 

 cells in detail, — in the Destruction [Enthildung), and 

 Reconstruction {Neubildung) of cells. 



I. FORMATION OP THE CELL. 



Cell-formation is one of the most essential peculiarities, 

 one of the most constant characters of the plant. In 

 cell-formation, especially, the vegetable organism shows 

 itself to be determined in its formation from within ; 

 through this the plant cuts off its structure, as a whole, 

 as in the smallest subordinate sphere of life, from with- 



