RHODOPHYCE, OR FLORIDEZ 241 
and the auxiliary cells (joint cells of ordinary thallus 
filaments) are associated together in fertile regions 
of the cortex. The gonimoblasts are very minute 
and numerous, and produce carpospores in nearly all 
their cells. The family, though a small one, is of 
general distribution, and is represented in British 
seas by the genera Petrocelis, Cruoria, Peyssonellia, 
Hematocelis, and Rhododermis. 
Corallinee. 
Of all Rhodophycece this family is the most easily 
recognised, from the strong incrustation of the thallus 
with carbonate of lime, producing a stony consistency. 
The different forms are, however, of the most various 
outward appearance. As in Nitophyllwm, so here the 
thallus filaments undergo subsequent intercalary 
divisions. Melobesia is of encrusting habit, like some 
of the Squamariee, growing by marginal initial cells, 
at first circular, but afterwards becoming lobed and 
irregular through unequal development.  Litho- 
phyllum forms thin stony plates of erect habit, while 
Inthothamnion gives rise to massive stony branches 
(Fig. 83). Starting from a stone or shell, which the 
thallus subsequently encloses more or less as a kind of 
core, its branches frequently form massive structures, 
in some cases almost rivalling the animal corals in 
bulk. They occur in particular abundance with the 
true corals, and the species of Lithothamnion, Melo- 
besia, &c., often act as a kind of mortar in holding 
together the reef-building corals. Corallina, Am- 
phiroa, Janta, and Cheilosporwm, are beautiful, stony, 
R 
