34. THE WORLD OF THE SEA. 
Their colour is olive, fawn, yellow, brown, more or less dark; 
green, more or less bright; pink, more or less delicate; carmine, 
more or less rich. | 
Some authors have divided them, according to their predo- 
minant colours, into three great sections :— The Brows, or Blacks 
(Melanosperms) ; the Greens (Chlorosperms) ; the Reds (Rhodosperms). 
The first are the most numerous. They can grow in a wider range 
of depth, and appear to occupy three distinct regions, forming the 
PLOCAMIUM PLUMOSUM. 
greatest part of the submarine forests. The green exist nearer the 
surface, often floating ; the red are met with in shallow water, on 
the rocks near the shore. 
If from the bottom of the ocean a submarine volcano heaved 
up an island of barren rocks and scoriz, the power of life would 
soon cover its surface with organisms. Almost as soon as the stone 
came in contact with the air it would become covered with little 
plants which, adhering to it, would round it, and little by little 
alter its shape. At first they appear only yellow or grey spots; 
then their colour changes to blue or green, and their construction 
alters, becoming more complex. As they grow older, the colour of 
these patches deepens, and their thickness increases. After the 
lapse of a certain time, they are covered with velvety threads; 
then they die, and from their decay spring other plants of larger 
size, a less stunted vegetation, and possessing more decided 
characteristics. 
