150 



100 



50 



-00 



73 



n 



m 



Z 



z 



(A 



o 



z 



150 



100 



50 



-00 



_l_ 



-8 



LOG lAA 

 G/ML. 



-7 



-7 



0^ 



o 

 tr 

 o 





LU 



O 



' vO\|^^- 



LOG 2,4 -D 

 G/ML. 



Fig. 1. Growth responses of segments from roots grown in indole-3-acetic acid 

 solutions (10-" g/ml). A and B. Total extension in 48 hrs. of normal (open circles) 

 and lAA-grown (solid circles) segments. (A) Responses to lAA. (B) Responses to 

 S.^l-D. Vertical lines indicate the least signilicant dilference (5 per cent) between 

 means. C and D. Epidermal cell length distribution before and after 48 hrs. of 

 extension. (C) Normal segment responses to I.\A. (D) L\A-grown segment responses 

 to I A A. Open parallel lines — segments inunediatcly after excision. Blacked-in 

 parallel lines — segments after 48 hrs. in 0.5 per cent sucrose solution. These lines 

 are plotted at distance of <t/\/N above and below tlie respecti\e mean of succes- 

 sive groups of cells. 



