'230 Relations between Growth and Environment 



(a) Effect of restricted food supply on total growth. 



It was to be expected that the unchanged set would make less growth 

 than the others, but the comparative relations of the amount of growth 

 at different periods of the life of the plant are not altogether what were 

 anticipated. As the plant grows and steadily draws on the limited food 

 supply, the available amount of nutrient in the solution correspondingly 

 decreases, and it might have been expected that with this decrease in 

 available food a gradual decrease in growth would occur, giving a curve 

 of the form 



This, however, did not occur in any case. At all seasons of the year the 

 growth in the earlier part of the second period showed a steady rise. In 

 winter when growth was very slow the rise continued throughout the 

 experiment; as the temperature and sunshine increased the time got 

 shorter until eventually the rise reached its maximum in about three 

 weeks. Then, quite abruptly, the growth changed and the curve flattened 

 to a greater or less degree, but when once the change had occurred steady 

 increase was again made, so that in most cases the curve took the form 



In the early summer months growth ceased before the end of the 

 experiment, causing a second flattening in the curve, whereas in the 

 height of the summer no further growth was made after the first rise 

 and a later drop often took place on account of loss due to respiration 

 and desiccation. 



Early sumiiu'i. 



Height of summer. 



