

ROOT HAIRS AND GROWTH 



357 



high degree of sensitivity to small changes 

 in the reaction medium. No data are 

 given as to the percentage of root hairs in 

 each solution in which the organization 

 given as typical occurs. It is also to be 

 observed that Strugger used roots which 

 were severed from the rest of the seedling 

 and then transferred to the solution. It 

 has been found (iz) that transfer of the 

 root to the solution from air has a marked 

 effect upon the development of the hairs, 



intervals. No relation between vacuolar 

 organization and hydrogen ion concentra- 

 tion was detected. In each solution there 

 was a considerable range of variation in 

 this regard. Even in the same hair there 

 was a change found (fig. z (b)) from time 

 to time, changing visibly in the course of 

 one or two minutes. It was furthermore 

 found (fig. z (c)) that the development of 

 an isolated vacuole in one of the hairs of a 

 duplex may be accompanied by cessation 



r\M 



c. 



Fig. z. Root Hairs Showing Relative Positions and Variations in Vacuoles 

 The series (b) was drawn from the same hair at intervals of a few minutes. The series (c) also shows the 

 vacuolar condition during the development of a duplex hair. 



which varies with time after immersion. 

 It would be surprising if severing the root 

 from the seedling would not have even a 

 greater effect upon the behavior of root 

 hairs. 



The writer (zi) has studied in collards 

 the vacuolar changes in root hairs which 

 developed on the attached root some hours 

 after immersion in solution of simple cal- 

 cium salts. They were studied over a 

 range of hydrogen ion concentration from 

 ]pH 4.5 to 1 1. 5 at one or one-half pH unit 



of growth, while the other hair with a 

 vacuole formed as an extension of that of 

 the cell proper would continue to elongate 

 at the normal rate. This indicates that 

 the vacuoles may operate in much the 

 same way as the nuclei in setting up cross 

 currents, due to their position, which 

 divert the main stream of materials from 

 the tip by means of a short cut back to the 

 cell proper, and thus bring about retarda- 

 tion or cessation of growth. 



Schaede (71) has studied the root hairs 



