THE WONDERS OF THE SHORE. 193 
coralline, the dark purple ragged dulse (Rhodymenia), 
the Carrageen moss (Chondrus), and above ail, the 
commonest of all, the delicate green Ulva, which you 
will see growing everywhere in wrinkled fan-shaped 
sheets, as thin as the finest silver-paper. The smallest 
bits of stone are sufficient, provided the sea-weeds 
have hold of them; for they have no real roots, but 
adhere by a small disc, deriving no nourishment 
from the rock, but only from the water. Take care, 
meanwhile, that there be as little as possible on the 
stone, beside the weed itself. Especially scrape off 
any small sponges, and see that no worms have made 
their twining tubes of sand among the weed-stems ; 
if they have, drag them out; for they will surely 
die, and as surely spoil all by sulphuretted hydrogen, 
blackness, and evil smells. 
Put your weeds into your tank, and settle them at 
the bottom; which last, some say, should be covered 
with a layer of pebbles: but let the beginner leave it 
as bare as possible ; for the pebbles only tempt cross- 
grained annelids to crawl under them. die, and spoil 
all by decaying: whereas if the bottom of the vase 
O 
