REJUVENESCENCE IN NATURE. 121 



processes in the cells themselves, through which their 

 arrangement is determined, as well as the forces with 

 which the organism works ; in a word it includes at its 

 final point the Physics of Organization, of which botanical 

 science has at present scarcely a foreshadowing. There- 

 fore, everything at its proper time! 



III. CELL-FORMATION. 



In proceeding to the subject of Cell-formation, we pass 

 over a series of phenomena of Rejuvenescence which 

 should be intercalated between the second and third 

 sections, namely, the processes of Rejuvenescence which 

 frequently occur in the development of the leaf itself, and 

 through which the leaf acquires its subdivision and com- 

 pound nature, as well as the Rejuvenescence of growth 

 also occurring in the ulterior completion of the parts of 

 the leaf, of which we have spoken already in examining 

 the leaf;* we farther pass over the phenomena of Reju- 

 venescence in the later completion of the stem, which 

 occur both in the longitudinal growth and the increase of 

 thickness, the former especially as intercalary growth of 

 the internodes,f the lateral as periodically renewed 

 growth of the cambium zone of the stem, between the 

 wood-mass and the bark, whereby originate the annual 

 rings in the trunks of the Coniferous and Dicotyledonous 

 trees. All these, as well as the already examined phe- 

 nomena of Rejuvenescence, necessarily lead finally to the 

 consideration of the cell, as the simplest sphere of 

 formation in the course of the life and growth of the 

 plant, from which all development starts, which in infi- 

 nitely varied repetition and modification accompanies the 

 entire development, and to the independent representa- 

 tion of which the conclusion of the development once 



* See page 113. 



t See Grisebacb, ' Ueber das Wachstlium der Vegetatioiisorgaue,' Wieg- 

 manu's 'Arcbiv,' 1843, i, 267. 



