RHODOPHYCEA, OR FLORIDEA 247 
from the colour of the chromatophores, which is in 
perfect agreement, but this is of purely physiological 
significance. On the other hand intercalary divisions 
occur in the cells of the thallus of Bangiacew, and 
though these occur also in Nitophyllum, Corallinew, 
&c., the argument is not in favour of inclusion on 
this ground. The pits between the thallus cells of 
Rhodophycee are also absent from Bangiacee. Beyond 
colour therefore there is little support to be gained 
from the character of the thallus in favour of 
inclusion. 
The Feproductive Organs—The cells that become 
the female reproductive organs are indistinguishable 
from the ordinary thallus cells. The process of special- 
isation consists in a slight increase in size, but of no 
particular alteration in shape, except the acquisition of 
avery short lateral protuberance, called the homologue 
of a trichogyne by those who favour the inclusion of 
the order among the red seaweeds. The antheridia 
produce motionless unciliated pollinoids. In Ery- 
throtrichia one of the thallus cells produces a small 
superficial cell, which is segmented off and becomes 
the mother-cell of a pollinoid. There is here a certain 
resemblance to the Rhodophycee, but in Bangia and 
Porphyra the pollinoids are produced by the repeated 
division (in all directions) of one of the thallus cells 
which has gradually lost its colour. Numerous small 
pollinoids are thus produced and set free by the dis- 
solution of the membranes of the parent cells. The 
pollinoid fertilises the female cell on attaching itself 
to the short protuberance (trichogyne). An open 
communication is effected, and the contents of the 
