ARTICLES 61 



tective influence. But notwithstanding this, there are a large 

 number of plants which are intolerant of this salt except in 

 the smallest amounts ; such plants will never be found growing 

 in a salt marsh. On the other hand, many plants can and do 

 flourish in soils which are excessively saline. Between these 

 two extremes plants of an intermediate constitution obtain ; 

 and in some cases it appears that plants normally intolerant 

 may be educated to endure certain salts. Thus Strange 1 found 

 that the cells of the root-tip of the white lupin and of the scarlet 

 runner quickly died if placed directly into a solution of -5 per 

 cent, potassium nitrate ; but if they were placed in water and 

 the salt added so that the concentration was gradually in- 

 creased, they could endure a strength of 1 per cent, without 

 succumbing. With regard to the limits of endurance of salt 

 marsh plants, Halket 2 found that Salicornia ramosissima and 

 Suceda maritima could withstand the presence of 17 per cent, 

 of sodium chloride in the soil water. 



Typical maritime plants can not only live in such highly 

 saline soils, but may require a certain amount of sodium chloride 

 for their normal development. 



The series of water and other cultures carried out by Halket 

 showed that species of Salicornia grow better in the presence 

 of sodium chloride than in its absence, the most luxuriant 

 growth taking place when 2-3 per cent, of this substance is 

 present. The results obtained for Salicornia oliveri are graphi- 

 cally shown in Fig. 1. 



On the other hand, Suceda maritima is more indifferent, 

 growth being as vigorous with as without the salt, provided 

 that not more than 1 per cent, obtains. If present in greater 

 amounts, the growth of the plants is proportionately diminished. 



The permeability or otherwise of membranes, with regard 

 to a definite substance, may differ not only in different plants 

 but also in the different cells of the same plant, so that no 

 general rules can be laid down. With regard to sodium 

 chloride, the plasmatic membranes of the cells of maritime 

 plants generally are permeable, and the same is true for a 

 good many other plants. For instance, De Vries found that 

 the beetroot is permeable to common salt, but this is hardly 

 surprising since this plant in its natural state is maritime. 



1 Strange, Bot. Zeit. 50, 253, 1892. 



2 Halket, Ann. Bot, 29, 143, 191 5. 



