138 THE SCOTTISH BOTANICAL REVIEW 



main disadvantage accruing- to flooded alluvial tracts being 

 the local tendency to stagnation and soil acidity. Their 

 physical relations to drainage are moreover detrimental to 

 deep root oxygenation, and the tree growth is generally of 

 short stature in temperate regions and confined to certain 

 species (13). 



When the deposits are well supplied with ground water, 

 but porous and superficially well aerated, meadow prevails in 

 temperate climates ; where less permeable and ill-drained, 

 marsh-land or swamp. The type of meadow naturally 

 varies with the physiography and the nature of the waters. 

 In the moorland region of this country a subxerophytic type 

 of grassland is commonly met with, but our lowland meso- 

 phytic meadows have nearly all been much altered through 

 drainage and cultivation. Extensive natural mesophytic 

 meadows are said to still persist in Northern Russia and Asia, 

 and form the habitat of some of the most striking species of 

 herbaceous Umbelliferae (i). 



Reed-swamp is generally confined to a narrow fringing 

 reed belt in our rivers, owing, no doubt, partly to artificial 

 restrictions to the lower river courses, but extensive reed- 

 swamps are widely distributed, according to Warming, and 

 consist of such genera as Phraginites, Glyceria, Cyperus, 

 Typka, and Sagittaria, and in tropical countries, of species 

 of Caladium^ HelicoJiia, Crinuni, and others (13). Alder 

 swamps and sallow swamps, according to the same authority, 

 are universal in north temperate regions. And there, also, 

 sallows and poplars fringe the streams in the steppes, while 

 thorn forest forms a characteristic belt to those of desert 

 subtropical zones. Black-gum swamps with Nyssa and 

 Taxodium have been specially studied in the forest regions 

 of the United States, and show peculiar conditions of the 

 lower parts of the trunks and of the roots of the trees, the 

 latter having a striking resemblance to the knee-roots of the 

 mangroves of the coastal swamps. 



In tropical countries, forest swamps of various species of 

 palms, bamboos, and aroids have been described. According 

 to Schimper, " Kurz states that swamp forest is the most 

 curious forest in Burma, and of great interest to the botanist. 

 In fact, its constituent plants are so dissimilar to those of the 



