246 SEAWEEDS 
enclosed within a common cystocarp wall,with a single 
apicalopening. As has been said, the antheridia and 
tetraspores are produced within similar conceptacles. 
The tetrasporangia arise at the base of the cavity, and 
either surround a central sterile bundle of filaments, 
or they occur in groups, separated by a wall of 
tissue from each other, and each with a separate 
apical pore (Melobesia). 
BANGIACEA. 
General Characters—The thallus consists of cell- 
filaments (Bangia), or flat plates of one layer of cells 
and of irregular outline. Male reproductive bodies 
without: cilia are produced within cells of the 
thallus, and they fertilise female cells specially 
distinguished from the thallus cells only by a short 
lateral protuberance. Non-sexual reproduction is 
effected by spores produced by the thallus cells, 
sometimes singly, sometimes after division of the 
parent cell. 
There has been so much discussion as to the 
systematic position of the Bangiacew, and with so 
uncertain a result, that the terminology of the repro- 
ductive bodies is difficult of application. The claim 
put forward for their inclusion among the Rhodo- 
phycece does not appear to be fully established, while 
at the same time there is no little difficulty in 
assigning them a place among the Chlorophycew. 
The Thallus.—The main argument for the inclusion 
of the Bangiacce among the Rhodophycee is derived 
