1909] OLSSON-SEFFER— VEGETATION ON SEA SHORES 93 



' IV. Beach at Pialba, Queensland, on the eastern coast of Australia, June 1 7, 

 1901. Atmospheric temperature 16 C. Sky clear. Velocity of wind about 

 6 m a second. Muslin exposed 5 m from the water. A heavy surf was rolling at 

 the time, but as the water is shallow far out from shore, and sheltered by clumps 

 of mangrove, the breakers did not strike the shore with any force. The sample 

 showed a salt content of 4.1 per cent. Salinity of ocean water 2.91 per cent., 

 and temperature g°4 C. 



Although the presence of sodium and chlorine, as common salt, 

 can be shown in many inland plants, a larger percentage of these salts 



marine 



former 



Whether these salts are absolutely essential for any plant we do not 

 know for certain. If that is the case, the amount of salt needed is very 

 small, as has been shown by several investigators. Even for many 



marine algae only the smallest quantities of salt are necessary, it at 

 all essential. 



Inland plants are, however, unfavorably influenced by a percentage 

 of salt which strand plants bear without injury; on the other hand, it 

 has been proved by cultures, that the halophytes can grow without the 

 usual amount of salt contained in the soil or atmosphere of their 

 natural habitat. 



An interesting experimental study of strand and other plants with 

 relation to common salt and sea water has been made by Coupin (5) . 

 H e found that 1.5 per cent, of common salt in soil or in water is 

 Poisonous to plants which do not naturally grow on the sea shore. 

 Sea water contains about 2.5 per cent, of common salt, and the soil 

 washed by the sea, as well as the atmosphere near the coast, contains 

 still more than this proportion. We can thus readily understand the 

 sharp line which separates the marine and strand floras from those of 

 the interior. Coupin attributes the poisonous property of sea water 

 lnland Plants mainly to its content of common salt, for the two 

 next to this in abundance, magnesium sulfate and magnesium 



alts 



c l °nd, are present in quantities which he considers below the toxic 

 Proportions. Magnesic sulfate is poisonous at a concentration of 1 

 Per cent > magnesic chlorid at 0.85 per cent., but they occur in sea 

 j^ter only to the extent of 0.75 per cent, and 0.5 per cent, respec- 



The ^estion of the influence of salt on strand plants and of the 



