164 



THE GERM-PLASM 



which is perfectly definite. The primary constituents of the 

 entire new shoot are contained in this group, and it is possible to 

 predict what parts of the shoot will be formed from each of its 

 cells. The successors of this group of cells continue to multiply 

 up to a certain limit, and have then only to become elongated in 

 one or more directions, and more highly differentiated, in order 

 to give rise to a fully developed • person " of the stock. This 

 person does not undergo any further essential changes, but it 

 is capable of giving rise to a new person from its apical cell ; 



Fig. 7. — The apex of a shoot of Ckara, in longitudinal section. (From Sachs' 

 ' Lectures on the Physiology of Plants.') 



for the latter is always being renewed, or. in other words, 

 it always remains the same. 



Let us take as an e.xample the alga Chara. A glance at Fig. 7 

 will at once make it apparent that the idioplasm of the apical 

 cell (t') cannot undergo separation into different groups of deter- 

 minants in the first division, because one of the resulting two 

 cells remains as the apical cell, while the other, or 'segmental 

 cell,' gives rise to an entire shoot, — that is to say, to that very 

 structure which the apical cell is capable of producing. The 



