, 
THE PLANES OF LHE SLA: 37 
and Scotland, and grows in such thick masses that the navigation 
of many of the rivers and canals threatens to be impeded. 
One of the characteristics of these ocean prairies is the simplicity 
of their composition. On land it is very different. Here we find a 
great number of different plants; but in an ocean prairie there are 
seldom more than two or three species, and very often only one. 
But these floating prairies are less numerous and less remarkable 
than the land prairies. 
The bottom of the sea is overspread with a covering of rich 
vegetation ; the plants are close together, and mingling their varied 
CALLITHAMNION. 
tints, they cover the ocean floor with a many-coloured carpet. 
Here are thickets and groves, gardens and woods. Upon the land 
there are but few virgin forests, but beneath the waves none are 
trodden by the foot of man. The marine vegetation is better pre- 
served, better protected than that on land. Terrestrial forests men 
mutilate, explore, root up, and burn, but they approach very 
timidly, with many precautions, and only for a few minutes at a 
time, the woods of the ocean. The submerged hydrophytes mingle 
their foliage loosely or interlace with each other firmly ; now they 
form arched grottoes, winding galleries, or impenetrable thickets. 
There is in the harmony of the vegetation of the sea a splendour 
