200 SOME MINOR PROBLEMS CONCERNED IN THE LOCAL
and their possibilities great, it does not follow that they are always
successful. A few illustrations may be quoted. In the Chelmer at
Felstead, at a certain place there grow Yellow Water-lilies and a
species of large Rush. These have retained their situation for more
than thirty years ; but they have made no progress either up or down
stream during that time, thus showing that, although they have flow-
ing water agency continually at hand, they certainly do not always
use it. In careful and long-continued examination of the floating
debris of the river at flood time, I have found but very few seeds of
any kind. In the river silt, which is periodically removed from the
bed of the river here, seeds are also rare. Those occurring most
frequently (indeed I do not remember to have observed others)
are Bistort, Comfry, and Teasel, inhabitants of the river's bank.
In The Essex Naturalist (vol. vi., page 76), mention is made
of the Water Soldier (Stratiotes) as being an inhabitant of a certain
pond at Saling during the last fifty years. None of the various
agencies for seed dispersal appear to have been brought into play
in that case for a very long time. Near Leighs Priory, there grows
a variety of Oak with curiously gnarled branches, some specimens of
which must be from two to three hundred years old, I do not
remember to have seen any trees with exactly their peculiarity further
than about a mile from that centre, and should say that all now
living are connected by descent. If that be the case, we must put
the acorn down as sometimes a slow traveller. Some field crops,
(clovers, etc.) of fifty years' standing, have not yet succeeded in
establishing themselves by the wayside. Many more instances
might be quoted of this partial or slow distribution, which is
perhaps connected especially with those plants the seeds of which
have no special adaptation for diffusion. In those plants having a
feathery pappus, and eminently adapted for wind-agency, the
opposite state obtains, they being widely and equally diffused.
This is well illustrated by the growth of thistles this year, which
are to be found in meadows and fields alike, a vast multitude.
This incalculable element of diffusion is still further complicated
by curious anomalies. Some plants do not even produce ripe seeds,
but depend upon certain other offshoots for the perpetuation of their
species. This obviously excludes some of the agencies for their
diffusion, and would, one would think, tend to their extinction.
The Horse-radish (Cochlearin armoracia) belongs to this class. A
cottage garden here was ploughed up many years ago, in which was