216 C. M. CHILD. 



The appearance of rhizoids or rhizoid-like structures on the 

 older, more basal parts of the axes, is a characteristic feature of 

 various species of algae and in some cases these structures are so 

 numerous as to form a more or less continuous cortical layer on 

 such parts. In Dasya, for example, where such a secondary 

 cortex formed by rhizoids is present on the older portions of the 

 axes, the cells of this region show a relatively low susceptibility. 

 In short, the rhizoid appears to be a structure originating at the 

 lower levels of an axial metabolic gradient, though of course 

 external conditions may determine whether or not rhizoids shall 

 develop at levels where their development is possible. 



Some of the experimental evidence presented below, as well 

 as the alteration and reversal of the primary intracellular gradi- 

 ent in the more basal cells indicates very clearly that the degree 

 of axiate individuation, i. e., the permanence of the primary meta- 

 bolic axial relations and their effectiveness in maintaining a par- 

 ticular order is not very high. Moreover, the short length which 

 the axes attain, the slight connection between the cells, the 

 irregularity of branching and the above-mentioned development 

 of rhizoids from any level of the more basal cells all support this 

 conclusion. 



If physiological polarity is primarily a metabolic gradient in 

 protoplasm, such a form as Griffithsia should be favorable material 

 for the experimental obliteration of old axes or gradients and 

 the establishment of new ones. The experiments described 

 below, which are suggestive rather than conclusive, constitute a 

 first step in this direction. 



EXPERIMENTAL OBLITERATION AND REVERSAL OF THE GRADIENT 

 IN RELATION TO INDIVIDUATION. 



The fact that obliteration or reversal of the general axial 

 gradient of Griffithsia usually occurs during the first few days 

 in the laboratory, even where the plants are kept in running 

 water, has been noted in an earlier paper (Child, 'i6e). The 

 results of a few simple experiments along this line remain to be 

 considered. 



Confinement in a limited supply of water without change in a 

 closed flask without air was used as an extreme degree of " bad" 



