ARTICLES 67 



with, all the root-hairs were strongly plasmolysed by a 3*5 

 per cent, solution of sodium chloride. The seedlings were then 

 rinsed in dilute saline and were gradually brought up through 

 successive concentrations to a 3-5 per cent, solution in which 

 they were allowed to remain for some little time. The root- 

 hairs of all the seedlings but one showed a complete recovery, 

 and exhibited no plasmolysis. The root-hairs of the one 

 seedling which did not show recovery were proved by subse- 

 quent investigation to be either dead or in a condition of very 

 low vitality, so that the negative results afforded by this 

 seedling in no way invalidated the positive ones given by the 

 other individuals. 



It is, therefore, seen that the root-hairs can raise their 

 osmotic strength as the salinity of the surrounding soil-water 

 increases. The two results show that the osmotic power of the 

 cell-sap of the root-hairs can be accommodated to that of the 

 soil. Incidentally it may be remarked that this adjustment 

 of the internal osmotic pressure in correlation with the external 

 conditions was subsequently found to obtain in desert plants 

 by Fitting. 1 



In addition to this fundamental fact, other observations of 

 less importance were made. It was found that when the roots 

 of seedlings taken from a very salt soil were plunged sud- 

 denly into fresh water some root-hairs burst, while others 

 swelled up at their tips in many curious ways. The explana- 

 tion is obvious : the osmotic strength of the root-hairs was 

 adapted to the surrounding high salinity ; when plunged into 

 fresh water there would be a sudden and relatively great 

 absorption of water, so that if the cell-walls were not suffi- 

 ciently strong to withstand this sudden increase in the internal 

 hydrostatic pressure the cells would either burst or swell up 

 considerably. 



This is a well-known phenomenon : thus Noll found that 

 Bryopsis, if taken from a rock-pool and suddenly plunged into 

 fresh water, would burst ; Lindforss ascertained that the 

 pollen grains of many plants would do likewise when placed 

 in water ; Curtis observed that moulds grown in concentrated 

 solutions and then placed in water burst at the tips ; also uni- 

 cellular animals like Paramcecium behave in a like manner 

 when subjected to a similar change of conditions. 



1 Fitting, Ztitschr. Bot. 3, 209, 1911. 



