Phyletic, Somar tar chic and Somatic Cell-Divisions 107 



omia, grown cells also take part in the callus- formation, 

 but, as it seems, only in a subordinate way. Perhaps by 

 far the greatest part of the somatic cells of plants have 

 this power in their youth, and the line of demarcation 

 between secondary germ-tracks and somatic tracks would 

 lose still more of its distinctness through this possibility. 



p. Phyletic, Somatarchic, and Somatic Cell-Divisions 



We will now look a little more closely into the cells 

 themselves, which are distributed along the individual 

 tracks. In the homoplastids all the cells and all the cell- 

 divisions have the same importance. The two daughter- 

 cells evolved from one mother-cell are of the same value. 



But in the higher plants such processes are relatively 

 rare. They happen chiefly only where a germ-track di- 

 vides into two equivalent branches, or where a uniform 

 tissue is deposited on a somatic track. By far the greatest 

 number of divisions, however, furnish unlike products, 

 and to this fact is due the entire differentiation. 



It seems more important to me to distinguish between 

 phyletic, somatarchic, and somatic cell-divisions. Those 

 divisions in which a germ-track-cell splits into two 

 daughter-cells, both of which, although in different ways, 

 continue the germ-track, are obviously phyletic. All the 

 somatic cell-divisions are divisions on the somatic tracks. 

 Where a track is laid down of such a nature that through 

 the division of a cell of the germ-track, there develops, on 

 the one hand, a cell which continues the germ-track, and 

 on the other hand, a somatic cell, the division is soma- 

 tarchic. 



There can be no doubt that, in the phyletic divisions, 

 the hereditary factors are transmitted to the two daughter- 



