126 SEASIDE PLANTS. 



plasmic contents of the unbroken cells contract and withdraw 

 from the cell-walls, the space between the walls and the con- 

 tracted cell-contents being occupied by the solution of salt. In 

 fact the living protoplasm is unable to absorb the salt and has 

 actually to give up some of the water with which it is saturated 

 to the hygroscopic salt-solution around it. If, on the other hand, 

 we kill the protoplasm, by boiling or by the application of acid, 

 before applying the salt solution we find that the latter diffuses 

 readily into the dead cell-contents and there is no such contrac- 

 tion as in the first case. 



This indicates that plants whose roots are supplied with 

 salt-water are able to assimilate for purpose of nutrition but a 

 very little of the water which reaches them : they are to a great 

 extent subjected to a water famine ; and they have developed — 

 in many different Natural Orders — water-saving structures. 

 Chemical analysis shows us that the plants have no choice in 

 this matter. As the sea water is rich in salts of soda, so tlie ash 

 of these sea-side plants is rich in soda ; but it can readily be 

 demonstrated that most, if not all, of this soda is physiologically 

 useless to the plant, which cannot, however, refuse to absorb it. 

 Not only do experinients in growing plants in prepared solutions 

 demonstrate that they can maintain their full health and vitality 

 while dispensing with soda ; but when a sea-side plant, such as 

 Asparagus, which occurs on another part of our Essex coast, is 

 transferred into ordinary inland garden mould, which is rich in 

 potash but poor in soda, the soda in the plant-ash rapidly 

 becomes replaced by potash. It is, however, important to bear 

 in mind that the converse of this experiment, the replacement of 

 potash by soda, cannot be performed, some potash being appar- 

 ently essential to the life of every flowering plant. 



Succulence is not, however, the only adaptation to the 

 economising water of which we have seen examples to-day. In 

 several species of grass, such as the Marram [Psamma arenaria) 

 and the Ljine Grass {Elymus arenarius), which grow near the sea, 

 we find the leaves are rolled up and their surface, not only 

 " glaucous," or covered with grey bloom, but marked by deep 

 longitiidinal grooves. To these grooves the few stomata are 

 confined, and, in some cases, hairs lining the grooves would 

 seem to be a special contrivance to re-absorb the moisture 

 directly it has been transpired by the protected stomata. 



