Ch. XIV] THE HALOPHYTES 573 



occur in such places because swamp and bog waters are 

 both cold and acid, — conditions which only xerophytes can 

 endure. The typical waterside shrubs are Alder and Wil- 

 lows ; these are deliquescent forms with soft wood and many 

 fine roots, which they form easily above ground, especially 

 in running water. 



E. The Saline Habitats, and the Vegetation Forms 



CALLED HALOPHYTES. 



On the sea-coast the soil contains salt, from little to the 

 three per cent of pure sea water ; and even more occurs at 

 salt springs or in other special places. Its presence renders 

 osmotic absorption by roots more difficult, while in quantity 

 it injures the tissues, from which it cannot be excluded. 

 Correspondingly, the plants which grow in such places exhibit 

 xerophytic features, preventive of much transpiration, and 

 hence absorption. The vegetation of seashores and salt 

 marshes includes many xerophytic grasses, annual herbs, etc-, 

 and the following principal halophytes. 



Annual Succulents ; typified by the common Samphire 

 or Saltwort of our coasts, a stem succulent with rudimentary 

 leaves and wind-pollinated flowers (Fig. 389). Allied are 

 leaf succulents like Buda, Suaeda, etc. Mangroves, 

 familiar on tropical strands (Fig. 397) ; large, deliquescent, 

 broad-leaved, with xerophytic tissues, organs of root aeration, 

 vivipary of the seeds, and other notable adaptations to their 

 difficult habitat. 



F. The Acid Soil Habitats, and the Vegetation Forms 



CALLED OXALOPHYTES. 



These are places in which organic acids accumulate in the 

 soil, because drainage is defective ; for bacteria, which destroy 

 the acids, are inhibited by poor aeration or low temperature. 

 This condition obtains in bogs, heaths, and cold moors. 

 The acids render absorption of water somewhat more difficult 

 osmotically, and also are disadvantageous in the tissues of 



