Vl] MARSH AND AQUATIC ASSOCIATIONS 153 



plant formations the two swamps respectively must be referred 

 to. They can scarcely be placed in the aquatic formation, as 

 they do not occur in water nor do many of the species exhibit 

 marked hydrophytic characters. The plants of the swamps 

 under discussion are not the " helophytes " of Warming (1909 : 

 185), the latter being members of reed swamps, which are here 

 included in the aquatic plant formation (see page 154). The 

 plants of- the siliceous and calcareous swamps here alluded to 

 are obviously more terrestrial in character than the members 

 of reed swamps, and should probably be placed in the two main 

 formations of the district which, like the swamps in question, 

 occur on the siliceous and calcareous soils respectively. On 

 this basis, the swamps of the sandstones and shales would be 

 placed in the same formation as the oak woods, scrub, and 

 siliceous grassland ; whilst the swamps of the limestone area 

 would be placed in the same formation as the ash Avoods, scrub, 

 and calcareous grassland. This arrangement conforms with the 

 general edaphic conditions, the general floristic composition, 

 and the topographical position of the two kinds of swamps in 

 question (cf the summary on p. 215). These swamps and their 

 related vegetation are obviously allied to the "Formation der 

 Quellfluren" of the Swiss plant geographers (cf Riibel, 1911: 

 193). 



RuDERAL Marsh Species 



In addition to the species which are definitely members of 

 the swamps in the vicinity of springs, there are a number of 

 other marsh plants of the district which cannot be referred to 

 either of the preceding plant associations, and which in their 

 distribution remind one of the ruderal plants inhabiting dry 

 "waste places" and roadsides. Many of the marsh ruderal 

 plants are found in wet places on stream-banks liable to be 

 flooded in times of heavy rains ; but they also occur in any 

 kind of wet places to which their reproductive parts may 

 happen to get carried. They are usually found in the more 

 lowland localities, and they are more at home in the marsh 

 associations of the alluvial plains. The names of a number 

 of such plants are given on the next page ; but, in addition to 

 the following, several plants of the swamps also exhibit ruderal 

 or viatical tendencies : — 



