210 



LIFE S BEGINNING ON THE EARTH 



sibility that living tissue may send out rays which are 

 capable of inciting cell-division in another tissue near it. 

 The initial experiment of Gurwitsch was carried out with 

 a set-up in which two onion roots were held in close approxi- 

 mation, the one vertical, the other horizontal as indicated 

 in Figure 80. After standing for several hours, sections of 



Inducing onion root 



Fig. 80. Tracing Mitogenetic Rays in the Onion Root 



The tip of the horizontal root sends out rays which act upon the vertical 

 root. After an action of several hours we find in the vertical root a larger 

 number of cells in the region opposite the tip of the other root. Many 

 of these cells are still in the process of cell division. This effect comes from 

 a radiation emanating from the root tip as can be definitely demonstrated. 

 (According to Gurwitsch.) 



the vertical roots were made. A larger number of cells, 

 as compared with other regions, was then found in the 

 vertical root in the region opposite the tip of the horizontal 

 root. 



The same observation is made' if a thin sheet of quartz is 

 interposed between the two roots, or if the inducing root is 

 completely encased in quartz, but the effect disappears if 



