r. They
grow on the rocks, in pretty coloured tufts.

If you dive still farther, into the dark depths of the sea, you find
beds of ooze and slime, and rocks and weird fishes, but no plants. Why
is this? Like the land-plants, these sea-plants must have _light_. They
cannot grow in the blackness of very deep water. Can you guess why some
sea-weeds are green and others red? Those growing in the shallow water
of the shore are green, like land-plants, because the sunlight reaches
them. Only part of the light can pass through deep water; and so, in
these shady places, the sea-weed is reddish in colour.

[Illustration: SEA MAT.]

We see, then, that (1) green sea-weed grows by the shore; (2)
brownish-green sea-weed likes deeper water; (3) red sea-weed grows in
deep water; and (4) in very deep water there is no weed at all.

We must not forget the grass of the sea. It grows in narrow blades,
often a yard in length, and as wide as your thumb. It is not a sea-weed,
but a real flowering plant, which, for some reason or other, loves to
grow under water. It creeps in the sand and mud, with green leaves
growing up as thick as corn in a cornfield.

All these waving green leaves make large meadows in the sea; and
sea-snails, fishes, and crabs hide in it, just as all manner of living
things hide in the grass of our meadows. The proper name of this strange
plant is Sea Wrack. When dried, it is useful for packing up china, and
covering flasks of oil.

Now we come to the real use of sea plants. They are food for all the
hosts of small animals of the sea. These eat it as it grows; or else,
like the mussel and oyster, swallow the tiny scraps of it which float
everywhere like so much dust.

The shell-fish, and other animals which feed on sea plants, are
themselves eaten by other sea creatures, and these in their turn are
eaten by crabs, lobsters and fish, which are eaten by us. It reminds you
of a chain. The first link in the chain is the sea plant, the last links
are the fish and ourselves. So, you see, the weeds and grass of the
ocean are of very great value indeed.

EXERCISES

1. Give the names of three common Sea-weeds.

2. What is the colour of the weed found in deep water?

3. Why cannot Sea-weed grow in very deep water?

4. In what way are sea plants most useful?

LESSON IX.

THE JELLY-FISH.

Or all the queer children of Nature which live in the sea, the
Jelly-fish is one of the queerest. You often find it