The sedge fringe in the shallows, the "haunt of coot and tern" elsewhere,
and of hosts of moorhens and dabchicks on the now protected river, is
mainly composed of the giant rush, smooth and round, which the water-rats
cut down and peel to eat the pith. These great rushes, sometimes ten feet
high, _die_ every year like the sickliest flowers, and break and are
washed away. Few people have ever tried to reckon the number of kinds of
sedges and reeds by the river, and it would be difficult to do so. There
are forty-six kinds of sedge (_carex_), or if the _Scirpus_ tribe be
added, sixty-one, found in our islands. They are not all water plants, for
the sand-sedge with its creeping roots grows on the sandhills, and some of
the rarest are found on mountain-tops. But the river sedges and grasses,
with long creeping roots of the same kind, have played a great part in the
making of flat meadows and in the reclamation of marshes, stopping the
water-borne mud as the sand-sedge stops the blowing sand. They have done
much in this way on the Upper Thames, though not on the lower reaches of
the river. The "sweet sedge," so called--the smell is rather sickly to
most tastes--is now found on the Thames near Dorchester, and between
Kingston and Teddington among other places, though it was once thought
only to flourish on the Norfolk and Fen rivers. It is not a sedge at all,
but related to the common arum, and its flower, like the top joints of the
little finger, represents the "lords and ladies" of the hedges. So the
burr reed, among the prettiest of all the upright plants growing out of
the water, is not a reed, but a reed mace. Its bright green stems and
leaves, and spiky balls, are found in every suitable river from Berkshire
to the Amur, and in North America almost to the Arctic Circle. In the same
way the yellow water villarsia, which though formerly only common near
Oxford, has greatly increased on the Thames until its yellow stars are
found as low as the Cardinal's Well at Hampton Court, extends across the
rivers of Europe and Asia as far as China. The cosmopolitan ways of these
water plants are easily explained. They live almost outside competition.