222 C. M. CHILD. 



THE DEVELOPMENT OF NEW AXES FROM ISOLATED CELLS IN 

 RELATION TO THE GRADIENT. 



One lot of Griffithsia, kept in running water for three days 

 after collection, was then placed in a shallow crystallizing dish 

 in one liter of water and left open to the air in diffuse daylight 

 without change of water. After two days in standing water 

 cell separation began apically, and after seven days had extended 

 over the whole length of the axes. Most of the cells were single, 

 but a few groups of two, three or even four cells were observed. 

 About half of the cells were dead at this time, the death rate 

 being highest among the cells from more apical regions. Almost 

 every one of the apical cells and probably 75-80 per cent, of the 

 first three or four subapical cells were dead. Taking the shape 

 and size of the isolated cells as an index of their approximate 

 level in the axis, it is evident that the proportion of cells killed 

 is greatest in the most apical regions and decreases basally, at 

 least, to the middle regions of the axis, below which the gradient 

 is slight, even under normal conditions. In short, the suscepti- 

 bility gradient of the axis is in evidence under these conditions 

 as well as in more rapid killing. 



After another week in standing water, examination showed 

 new growth and development in 10-15 P er cent, of the living 

 cells. Figs. 2 and 3 show cells from the more basal levels with 

 new apical cells at what were originally the basal ends. Sus- 

 ceptibility gradients were determined in both these cases, the 

 progress of death being in the direction of the arrows, the new 

 apical cell dying before the old, large cell and the intracellular 

 gradient in the large cell being in the direction of the arrow in 

 both cases. In many other similar cases similar gradients were 

 found and still other cases were observed without determination 

 of the susceptibility gradient. 



Fig. 4 shows a cell from the middle region of an axis, in which 

 a new apical cell has arisen at the original apical end. The 

 susceptibility gradient, both general and intracellular, is indi- 

 cated by the arrow which points in the direction in which death 

 progresses. Fig. 5 is a case in which a group of three cells from a 

 level near the apical end have remained connected. The only 

 new growth in this case is a rhizoid from the basal end of the 



