32 THE WORLD OF THE SEA. 
which adorn our woods and valleys. To begin with, they have no 
roots. Those which float are globular or ovoid, tubular or mem- 
branous, without any appearance of roots. Those which adhere 
are fastened by a sticky surface, more or less lobed and divided. 
They derive no nourishment from the earth; their growth is 
entirely from the exterior. Their whole existence they owe to the 
water: they receive everything from it, and return everything 
to it. 
The terrestrial plants take up from the earth, by means of their 
LAURENCIA PINNATIFIDA. CLADOSTEPHUS VERTICILLATUS. 
roots, certain nutritious matter, and they do not thrive unless 
the soil be suitable. Marine plants are utterly indifferent as 
to what they adhere to. It may be limestone or granite, it 
is all the same to them; hence they are found indiscriminately 
mixed. The same may be said of corals and shell-fish. These hy- 
drophytes possess neither true stems nor leaves; they expand by 
means of layers or lamels, broad or straight and narrow; of only 
one piece, or of many pieces, which take the place of leaves. 
They sometimes resemble wavy thongs, sometimes crumpled 
threads; some are thick and tough, others are thin and mem- 
