234 Priestley and Ever shed, — Groivth Studies. /. 
growth falls, and a relatively long straight part of the curve indicates 
a direct proportion between growth and time. Finally the curve is 
inflected and growth decreases exponentially with time until a brief almost 
flat portion terminating the first S curve suggests a temporary cessation of 
growth. 
Fig. 5. The dry weight ratio for roots from cuttings of 1 Princess of Wales ’ tomato. 
The arrow indicates the time of appearance of secondary roots. 
We would draw attention to the fact that this last flat region of the 
curve has obviously some connexion with the development of the lateral 
roots. In all the curves the point is marked upon the time axis where the 
occurrence of secondary or tertiary roots was noticed. These points are 
very definite, especially in the case of Tradescantia , where the lateral roots 
