286 THE SEA-WEEDS AT HOME AND ABROAD. 
on the Florida shores, of which, perhaps the 77. opuntia is 
the most common, as I have picked several fragments of its 
clustered stems from gorgonias aud corals collected among 
the Keys. Removing the lime encrustations, a singular skel- 
eton of fibres, branching off into clusters of smaller branches, 
presents itself and which serves as a support to the tissues. 
In company with these oddities is another singular marine 
produetion, composed of innumerable slender, single-celled 
Fig. 74. branching filaments, inextri- 
cably woven together into the 
form of a hollow ball, and 
whieh grows from the size of 
a cherry to that of the human 
head, and is known in the 
European seas as Codium 
C bursa, or Sea-purse; while 
another species with a nar- 
row, long, branching form, 
but with fibres similarly en- 
tangled and woven, has been 
found on the coasts of Cali- 
fornia, but is not known on 
the Atlantie shores of New 
England, a prize perhaps for 
Halimeda. some sea-weed collector! Of 
the other siphon-constructed alge may be cited the Cauler- 
pas, elegant, green, creeping-rooted algæ, mimicking under 
graceful forms, the ferns, club-mosses, feathery mosses, 
ground pines, selagines and other higher cryptogamic plants, 
such as grow in the woods and in bogs remote from the sea ; 
investing the submarine sands and tide-washed rocks with 
perennial verdure and loveliness, and found alike in every 
tropical sea on the globe. 
These lime-bearing alge so far away from our personal © 
observation, and to be seen only in our most southern lati- 
tudes, should have some representatives on our northern 
