RED SEAWEEDS 207 
(1) at such depths (where the light is greatly modified), 
and also (2) in waters of such considerable salinity. It 
is probable that this modification has masked their true 
relationship to other plants, as well as to one another. 
322. One ofthe lowest of the Red Algae is the common 
“Laver” (Porphyra), of the class BANGIOIDEAR, of all 
coasts, in which the erect, deep purple, leaf-like, and 
basally rooted, plant body is composed of a single layer 
of cells. They propagate by monospores borne in the 
cell layer. In their very simple generation certain cells 
of the cell layer divide into non-ciliated sperms, while 
others become very slightly modified into oogones, each 
containing a single egg. The latter is fertilized by the 
entrance of the sperm through an opening in the cell 
wall, after which the zygote develops into usually eight 
spores. The fruit is thus of very simple structure. 
323. In Nemalion (which with the succeeding plants 
belongs to the class FLORIDEAE), a branching, filamentous 
marine Red Alga, the clustered antherids 
produce small _ spherical, non-ciliated 
sperms. The oogone is prolonged into a 
slender structure, the trichogyne, and to 
this latter the sperm adheres and fertilizes 
the egg. After fertilization the egg divides, Fie. 91. 
and each new cell sends out short crowded 9 “°™™™°™ 
branches which bear terminal spores. Here no protec- 
tive envelope covers the spores, the fruit being very 
simple. Asexual reproduction is not known. 
324. Here may be noted briefly the Corallines (Coral- 
lina) which are filamentous Red Algae which become so 
heavily coated with lime as to effectually hide their cells. 
This lime coating is like an ancient coat of mail with its 
flexible joints at intervals. The antherids and oogones 
are in separate terminal cup-shaped structures, those con- 
