228 SEAWEEDS 
place with the auxiliary cell-and the nuclei of both 
unite. 
The formation of the wall of the cystocarp begins 
when the carpogonium has been fertilised and the 
auxiliary cell is recognisable. Branched filaments 
arise from the thallus-cells in the immediate vicinity 
of the one which bears the carpogonial branch, and 
their apices meet over the auxiliary cell and the 
whole body assumes a globular form. It is note- 
worthy that these filaments have no pore connections 
with the carpogonial or the auxiliary cell. They 
develop into the cystocarp wall, which at first so 
confines and presses against the swelling carpogonial 
and auxiliary cell that the contents of the wall-cells 
next adjoining die off and their membranes swell 
up. At about this stage the auxiliary cell, after 
union with the carpogonial cell, fuses with its parent 
cell, and the whole united cylindrical body extends 
a kind of foot into the thallus beneath it. It may 
now for convenience sake be called the central cell. 
From its apical region there are now produced a 
number of marginal (gonimoblast) cells which have 
pore-connections with the central cell, and each of 
these gives rise toacarpospore. The central cell pro- 
ceeds to unite below with cells of the thallus 
adjoining it, while it bears more gonimoblast cells 
on its upper and middle portions. In the ripe fruit 
only the outermost layer of cells of the wall remains, 
and these swell up and yield at the apex, permitting 
the egress of the carpospores. 
Minor differences occur in the allied genera Cham- 
pia and Lomentaria. Among these it may be noted 
