vi] 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 woods, 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 
Quelifluren” 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 :— 
