294 TRANSACTIONS OF THE [Skss. lxxtiii. 



hours, with the lengths of the growing' regions for that 

 period under the four sets of conditions above mentioned. 



Several experiments were carried on, and the conclusions 

 are based on these, but only one of each has been selected 

 as typical for the conditions given. 



These graphs show very clearly the increase and decrease 

 in length of the growing regions from day to day, following- 

 very closely in most cases the daily increase in the growth, 

 though no definite relationship can be made out between 

 them. 



All the curves are very similar in character. 



Description of the Graphs. 



G.R. — Lengths of growing regions every twenty-four hours. 

 G.I. — Growth increase every twenty-four hours. 



Plate XVIII. (I.) Under the Normal conditions the two 

 curves generally vary together in both organs, showing an 

 increase, followed by a slow decrease. 



(II.) Under Intermittent conditions the two curves of the 

 shoot vary together. 



In the root they vary together very closely at the begin- 

 ning, but the growing region curve flattens out more later 

 on. In the root the curves have only a downward portion, 

 probably due to the retardatory effect of light. In com- 

 parison with I. all the curves show a diminution in height. 



Plate XIX. (III.) Under the conditions of Darkness the 

 two curves of the shoot have a tendency to diverge from 

 the correlative variation so characteristic of the others. In 

 comparison with I., II., and IV., the curves bring out the 

 fact, previously mentioned, that the growth increases, while 

 the growing region decreases. 



In the root the two curves vary a little : the growth 

 increase curve first decreases, then increases, though not 

 to so high a point, then decreases again ; while the growing 

 region curve decreases and finally flattens. 



The growth curve in this particular case is as high as I., 

 but higher than II. ; while the growth region curve is less 

 than I. and II., but higher than IV. 



(IV.) In the Light continuously the two curves of the 

 shoot vary together and show that the growth is less than 



