VISIBLE CONSTRUCTIVE ACTIVITY IN PROTOPLASM. 583 



transmitted to the descendants. In the next generation oi: these same plants it is 

 a gi'oup of spherical and not of dodecahedral cells, which arises at the particular 

 place. The latter will, indeed, only reappear if the aforesaid pressures be again 

 exerted. 



How little, however, external influences define the foi-m and grouping of 

 permanent cells, is shown by the fact that from one and the same meristem, under 

 the same pressure, the same temperature, and equal illumination, arise in the closest 

 proximity the most different permanent cells; and that, on the other hand, the 

 formation and grouping of these cells is not essentially different when the develop- 

 ment of the meristem takes place under wholly different external pressure, or 

 different temperature. We always come back to this important thesis: — the forces 

 operating on plants from outside are only stimuli to the formative processes; 

 these latter are accomplished independently of external influences in a manner 

 established for each species, and founded in the specific construction of its living 

 protoplasm. 



