ee MARSH AND AQUATIC ASSOCIATIONS 161 
THE RELATION OF MINERAL SALTS TO THE FLORA 
AND VEGETATION 
It will be seen that the differences between the flora and 
vegetation of the calcareous and the non-calcareous terrestrial 
soils are paralleled by differences between the aquatic and 
sub-aquatic flora and vegetation. These differences cannot be 
explained by the differences in the physical nature of the 
habitat, for, in the case of the two aquatic habitats, the physical 
characters are identical. The facts therefore support the view 
that the presence of lime-loving plants in calcareous waters 
and soils is somehow related to the chemical composition of 
the waters (cf. Schimper, 1903: 102). Wheldon and Wilson 
(1907: 90) also point out that in addition to water-content, 
“another agent also has its influence. On examining the 
plant associations of habitats having about the same degree 
of humidity, we frequently find the species in them are totally 
dissimilar.” These authors then go on to give the groups of 
species found respectively in boggy ground at the calcareous 
shore of a moorland tarn, with Primula farinosa, Cladium 
Mariscus, Schoenus nigricans, Juncus obtusiflorus, and Hypnum 
falcatum ; of the swampy margin of a pool on the glacial drift, 
with Ranunculus Flammula, Bidens tripartita, Alisma Plantago, 
Sparganium neglectum, and Hypnum aduncum; of a peat bog, 
with Drosera spp., Andromeda Polifolia, Carex limosa, Myrica 
Gale, and Sphagnum spp.; and of estuarine marshes, with 
Spergularia media, Limonium (= Statice), Aster Trifolium, and 
Glyceria maritima. As “in all these stations the water supply 
is fairly constant and really in excess of plant requirements, 
and the conditions of altitude and exposure practically identical,” 
the authors “are led, therefore, to the conclusion that some 
component of the soil must be the factor which determines the 
presence or absence of these various species”; and it seems to 
me also that a study of the distribution of plants in any district 
where the chemical composition of the soil shows great varia- 
tions leads inevitably to the conclusion of Nageli (1865: 367), 
of Schimper (1903: 101), and many others that the chemical 
constituents of the soil, in addition to any or all of the physical 
M. 11 
