The plants themselves fall into four groups,
as was noted in Chapter III. Firstly the
floating plants, secondly the submerged oxy-
genating plants, thirdly plants rooting in the
soil but with their flowers and foliage out of
the water and, finally, plants with submerged
oxygenating foliage but with the flowers above
the water. In the following lists the last
group will be included with the oxygenating
plants.
Surface Floating Plants
The value of these usually insignificant
plants is really very great. Many small
creatures find sanctuary in the masses of
thread-like roots depending in the water and,
particularly as regards Duckweed, the fishes
derive great benefit from eating them.
Duckweed. Three kinds of duckweed are
found commonly in this country, the Greater,
the Lesser, and the Ivy-leaved. The latter
has the leaves in ivy-shaped fronds, in the
other two the leaves are separate. Duckweed
should not be introduced into large ponds or
lakes ; it soon covers the water with a green
coat that does not look altogether pleasant.
Frogbit. The leaves of this plant resemble
those of the water lily, but are much smaller-
up to two inches in diameter, in reality.
It has a small yellow flower and reproduces
itself by buds formed in Autumn which drop
off the plant and remain on the bottom until
the following Spring. Then they arise and
burst forth as separate plants. Fishes are very
fond of frogbit.
Riccia.
This plant grows
in a dense mass and is
considered a good oxygenator ; when the sun shines
on it large bubbles of
oxygen may be seen forming
within the mass. It is closely related to
the mosses.
Azolla.
Similar in colour
to Salvinia this so-called
' Fairy Moss ' grows in small
fronds about a quarter-inch
across. It is suitable either
for pond or aquarium and thrives best in
bright sunlight, when the edges of the fronds
assume a crimson tint. Azolla is one of the
most delightful of all the small floating plants.
Salvinia. Salvinia is suitable
only for the indoor aquarium or
greenhouse, being
a semi-tropical importation. The
leaves are pointed
oval-shaped and
are covered with
a fine down : the
colour is a delicate pale green.
Eichornia or Water Hyacinth. This beautiful
South-American
floating plant can be
grown in the indoor
aquarium or in a
bowl in the greenhouse ; it is not
quite hardy enough
to withstand the
vagaries of our Summer out of doors.
Spikes of lavender-
blue flowers arise
from a mass of thick leaves ; altogether a
most decorative plant. The roots hang down
in the water and provide shelter for fish fry,
etc.
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