284 BOTANICAL GAZETTE [OCTOBER 
falling upon them as rain, or derived from the melting snows in 
spring, must saturate the soil to considerable depths, if not to the 
bottom, thus bringing the water and minerals of upper and lower 
levels into continuity. Now there is no circulating ground water 
in the marshes, as the invariable failure of wells dug upon the 
marshes shows; furthermore they lie below the level of the fresh 
water of the bogs and mostly below the high-tide level of the sea, 
and hence there can be no under-marsh drainage, no more indeed 
than the surface drainage allowed by the shallow ditches or nat- 
ural runways. This lack of deep drainage has two important 
consequences; first, there is little or none of that loss of the 
valuable soluble mineral matters such as is constantly occurring 
on well-drained upland soils (a fact which alone goes far to 
explain the lasting fertility), and second, practically the only 
outlet for the water of the soil is by evaporation from the surface 
or transpiration through the plants, both of them necessitating 
an upward movement which tends to bring up the minerals from 
below. That this effect is actually produced by evaporation is 
shown by the fact that bald spots even on long-reclaimed, and 
hence long-drained, marsh always show an efflorescence of salt, 
and the same is true upon all freshly-exposed surfaces of marsh 
mud, no matter how long this may have been shut off from the sea. 
These facts can only be explained by supposing that the salt is 
brought up constantly from the greater depths. Further, practi- 
cally the entire vegetation of the marshes consists of the grasses, 
which both have a comparatively low rate of transpiration them- 
selves, and also protect the ground in an unusual degree from 
direct evaporation. Hence the upward movement is but slow, 
and when the warm summer sun promotes transpiration from the 
plants, the draft made upon the water of the upper soil is not too 
rapid to allow the latter to recoup itself from the lower layers, 
and that from a still lower, and so on, to a considerable or even 
great depth. This upward movement brings with it the minerals, 
which are not only thus being lifted towards the surface by the 
ascending water streams, but are constantly diffusing from the 
lower richer to the upper poorer layers. It can thus come about 
that the entire depth of the marsh soil is available to the vegeta- 
