Temperature on the Rate of Growth in Pisum sativum . 33 
The conclusions from Table II are (1) that the roots germinated and 
grown at a constant temperature (Expts. 9, 10, 11) show the Grand 
Period on the third day at 14 0 C., and on the second day at 23 0 C. ; (2) that 
roots germinated and grown for one day at a temperature of 15 0 to 17 0 C. 
and then transferred to a different constant temperature show the Grand 
Period also on the third day, but if they be transferred to a different higher 
temperature at the beginning of the second day, the Grand Period occurs on 
the second day. Thereafter, in all cases, the rate falls slowly to the time of 
appearance of the side-roots ; (3) that the side-roots appear at a definite 
length of the main root — in all cases except one, when the main root is 
between 80 and 90 mm. long. They therefore appear earlier, in time, 
at high temperatures than at low. This agrees with Askenasy’s results so 
far as the appearance of the side-roots at a particular length of the main 
root is concerned, but he found that the rate of growth of the main root 
maintained a constant value from the beginning of the Grand Period 
till then. 
Text-figs. 4 and 5 show the results of Expts. 9 and 10 respectively. 
With regard to the bearing of these facts on the experiments in general, 
all measurements, being made at the beginning of the third day of growth, 
are made in that phase where the rate of growth is, as nearly as possible, at 
its highest value and most constant. Further, as has already been deter- 
D 
