192 HELOPHYTES 



ward side of mangrove-swamp, from whose species it derives subordinate 

 constituents ; it also appears in connexion with lagoons and swamps, 

 but mostly on less saline soil. According to J. Schmidt ^ it does not 

 truly belong to the saline mangrove-swamp, next to which Schimper 

 places it, but rather belongs to fresh-water swamps along rivers. 



In the tropics several other, but httle known, forms of forest-swamp 

 and bush-swamp occur. A small fan-palm, a species of Bactris, clothes 

 large swampy tracts along the river Caroni on the plains of the 

 island of Trinidad. Another palm. Phoenix paludosa, is encountered in 

 eastern Asiatic swamps. While, according to Kurz, in Burma there 

 are swamp-forests that are leafless during the rainy season. Reorders ^ 

 gives an interesting account of a forest-swamp in the interior of Sumatra, 

 in which respiratory roots (in Calophyllum, Eugenia, and others), prop- 

 roots, plank-roots, and remarkable besom-like aerial roots (i-i|- metres 

 in length) occur. The physiological dryness and these peculiarities of 

 construction are to be attributed to lack of oxygen in the soil. 



It is impossible to establish any sharp distinction between swamp- 

 forests and forests on dry land ; this is shown by the semi-aquatic 

 varieties ('facies') of the primaeval forests that line the Amazon, which 

 are annually inundated, and are locally known as ' igapo '.^ 



Bush-swamp and forest-swamp occur not only in tropical and 

 temperate, but also in arctic lands ; for instance, in Kanin peninsula, 

 on the White Sea,^ Picea excelsa, Betula pubescens, and Pinus sylvestris, 

 occur as dwarfed trees on insufficiently drained soil, and are accompanied 

 by genuine marsh-herbs such as Eriophorum vaginatum. 



Again, in the rainy zone of the territory near the Magellan Straits 

 the forests composed of evergreen species of Nothofagus (N. betuloides 

 and others) are regarded by Dusen ^ as hydrophytic communities ; here, 

 extraordinary humidity brings forth a swampy soil nearly wholly carpeted 

 with mosses. In this, as in all other cases, sharp distinctions are lacking. 

 But it must be insisted that in these bush-swamps the soil is always 

 more or less sour (rich in humous acids), and that consequently this 

 formation is allied to the one about to be described.^ 



^ J. Schmidt, 1903. ^ Koorders, 1907. ' J. Huber, 1906. 



* Pohle, 1903. * Dusen, 1905. 



" W. G. Smith, 1903 ; N. Walker, 1905 ; see also, on the subject of this chapter. 

 Coulter, 1903 ; Hitchcock, 1898 ; Kearney, 1901. 



I 



