292 



TRANSACTIONS OF THE 



[Sess. 



Results. 



Table I. 



The above table, constructed from numerous careful 

 observations of measurements, gives the average lengths in 

 mm. of the growing regions of shoots and roots respectively 

 under various conditions. 



Reference to the figures will show that the varying con- 

 ditions have a direct influence on the length of the growing 

 region of both root and shoot. 



Any change from the normal conditions is accompanied 

 by a decrease in the growing region, which differs for each 

 condition, being progressively smaller for the root for the 

 conditions in the order stated in the table. There is an 

 exception for the shoot in the numbers III. and IV., which 

 are the reverse of the root. 



The figures in column III., considered in conjunction 

 with column I., prove that etiolation diminishes the actual 

 length of the growing region, and consequently that the 

 great elongation of an etiolated shoot is entirely the result 

 of increased growth activity and not in any degree con- 

 sequent on elongation of the growth region, which is, as 

 already stated, shorter than the normal. 



This is, contrary to Pfeffer's statement, 1 based on Strehl's 

 views that the growth region increases in etiolated shoots. 

 It will be obvious that the decrease in length of the 

 growing region under Intermittent light conditions is a 

 correlative effect due to interaction between root and shoot, 

 resulting from the exposure of the root to light during the 

 daytime. In Light the growing region of the shoot is less 

 than in the Normal, though it is larger than in the Dark, 



1 Loc. cit. 



