CHT.OROPHYLL AND GROWTH 139 



merited early in the unfolding stage, by food 

 formed by the young lamina. In a short time Ordinary course 

 the supplementary amount from the leaf is of growth 

 entirely sufficient for its own needs for con- 

 structive purposes ; and at this time the re- 

 serve food transported to the leaf has under- 

 gone great diminution. When a leaf is placed 

 under such conditions that the lamina is inac- 

 tive, the amount of reserve material which 

 can be transported to the leaf will, in many 

 instances, be found insufficient for its needs. 

 This will be best understood when it is 

 stated that the amount used at this time is 

 many times greater than that needed in the 

 earlier stages, and moreover, that the difficul- 

 ties of translocation have vastly increased. 

 Thus by the elongation of the petioles — 

 amounting from two to ten centimeters daily 

 in Arisaema — the distance between the stored 

 food in thecorm and the point of consumption 

 in the leaf-blade has been greatly exaggerated. 

 Then again the amount of stored food has 

 been materially reduced by consumption and 

 the intervention of destructive fermentations. 

 It is apparent without recourse to a further 

 recital of the detail of the experiments, that, 

 if at a time when the available food supply is 

 diminishing to a minimum, and the difficulties 

 attendant on translocation are becoming 

 greater, the needs of the leaf should suddenly 



