SEAWEEDS AND THE WATER-FLORA. 1 95 



poliuni, in some places the common Thrift {Aruiei'ia 

 vulgaris) and others. On the shoreside this vegetation 

 is ahvays being encroached upon by the regular seaside 

 turf, or by cultivation. Towards the water, these mud- 

 plants become more and more distant from one another, 

 until they finally disappear about, or a little below, the 

 level of high tide, just above the Ruppia zone. 



The most interesting point about these mud plants 

 lies in their being apparently adapted to dry conditions, 

 in spite of their living usually in places where there is 

 abundance of water. Many possess fleshy leaves, and 

 some, such as Cochlearia, occur also on the tops of 

 mountains, where, at first sight, it would seem as if the 

 conditions were totally different. 



The following is the explanation of the phenomenon 

 generally given. It is known that if ordinary plants, 

 such as the Daisy, are watered with salt water, the 

 leaves become more fleshy and succulent than usual. 

 The salt is a poison to vegetable protoplasm ; and it is 

 obvious that plants that grow near salt water should 

 diminish the amount of water they absorb as much as 

 possible, so that as little salt as possible should enter 

 their system. In this way the plants growing on the 

 margin of the sea acquire their peculiarly fleshy leaves 

 and their resemblance to dry climate plants. 



Many of these mud plants are very strongly attached 

 by thick and branching roots. This is necessary, 

 because they are often exposed to the full scouring 

 action of high tides. In places where the land is 

 being washed away, they may be seen invading the 

 domain of the ordinary grasses, and other associations 

 which are in process of being killed out by the salt 

 water. At a lower level than the Cochlearias (some- 

 times also between them), recently deposited mud 



