GROWTH 



281 



marking the growing organs by means of India ink applied with a 

 fine brush is used. These marks are made at definite distances 



Fig. 106. — Wiesner's auxograph {after Molisch). 



from one another and the increase in the distance is measured at 

 certain time intervals. This enables one to obtain a precise 



Fig. 107. — Two etiolated seedlings of the 

 horse bean with markings made 24 hr. 

 before photographing. On the right, a 

 seedling with markings just made (after 

 Nathansohn) . 



Fig. 108. — Maize sprouts 

 with markings made on 

 roots: a, before the experi- 

 ment; b, 24 hr. later (after 



Molisch). 



measurement of the change in length of each portion during the 

 experiment (Figs. 107 and 108) and to ascertain the dimensions of 



