22O C. M. CHILD. 



tory conditions (Child, 'i6e), like the earlier stages of confine- 

 ment, brings about a greater or less degree of physiological de- 

 pression which is greatest in the most sensitive parts of the 

 plant, the apical regions, and which, if sufficient, obliterates or 

 reverses the original axial gradient. In cases of confinement in 

 the small flasks as described, death usually follows this change 

 in two or three days at most, but where the change occurs less 

 rapidly, as in a large flask, in open standing water or in aquaria 

 with running water, the obliteration or reversal of the gradient 

 in the apical region is followed after two or three days by separa- 

 tion of the cells of the apical region in which the obliteration or 

 reversal of the gradient occurred. In short, after obliteration 

 or reversal of the gradient together with decrease in metabolic 

 activity, the axis falls apart into its individual cells or into 

 groups of two or three cells. This process begins apically because 

 this is the region where the change first occurs, but as time goes 

 on, if the environment does not improve, or if the plant is unable 

 to become acclimated as a whole, the change in the gradient 

 extends farther and farther in the basipetal direction and the 

 separation into cells follows it in the same direction. In plants 

 kept in open crystallizing dishes in a liter of sea-water without 

 change, cell separation usually begins in the apical regions after 

 several days and progresses basipetally, until after ten days most 

 axes are completely separated into cells or small cell groups. 

 In running water also cell separation usually begins in the apical 

 regions after several days and progresses basipetally, though 

 more slowly than in standing water or in a closed flask. In this 

 case, however, separation often ceases at some level of the axis 

 and the cells basal to this level maintain their continuity. The 

 apical beginning, the basipetal progress, and under the less 

 extreme conditions the halting at one level or another of this 

 process of cell-separation constitute still another demonstration 

 of the existence of an axial gradient in which susceptibility to 

 these conditions is greatest apically and decreases basipetally. 



This process of cell-separation is a reaction of the living cell, 

 and is not necessarily followed by death, although under con- 

 ditions in which any considerable degree of separation occurs, a 

 varying percentage of the cells, chiefly the cells of more apical 



