THE RED ALGA 487 
made up of cells still capable of division is termed a meristem, ' 
or is described as meristematic, while a fully differentiated 
tissue is distinguished as permanent. 
Laminaria reproduces only by swarm-spores which are formed in 
sac-like sporangia projecting from the surface of the pseudo-leaf. 
They are crowded closely, together with a number of curiously 
shaped protective cells called paraphyses.2_ The swarm-spores have 
a red eye-spot and two flagella which are attached at the side. 
There are no gametes. 
A somewhat higher development both of the vegetative and re- 
productive systems is found in the genus Fucus (Figs. 318, 319) 
which includes the common “bladder-wracks”’ of the sea-shore, 
so called because of the bladder-like floats (J) developed in the 
thallus. The meristematic tissue is at the tip of the thallus-lobes. 
A disk-like pseudo-root attaches the thallus to rocks which lie mostly 
between tides. The pseudo-shoot has forking midribs with flat 
expansions on either side in which the inflated bladders often appear. 
There is a rind and an inner, somewhat pith-like tissue much as in 
Laminaria. The tips of certain branches become swollen (s, Fig. 318) 
and produce a number of small cavities (conceptacles) each opening 
by a pore at the surface and lined with numerous paraphyses among 
which appear either male or female gametangia (Fig. 319, a). Within 
a female gametangium (6, c) eight large, spherical, non-flagellate 
gametes arise and are pressed out into the surrounding water by swell- 
ing of the paraphyses. The male gametangia, (d) expelled at the same 
time emit numerous flagellate gametes (g) which resemble somewhat 
the swarm-spores of Laminaria. They are attracted in large num- 
bers to a female gamete, and, attaching themselves to its surface, 
often cause the sphere to revolve by the energetic movement of their 
flagella (e). Directly after fertilization the odspore comes to rest and 
germinates (f), attaching itself to some rock by projections which 
form the beginnings of a pseudo-root, while the main part above 
becomes a meristem for the shoot. No swarm-spores are produced 
and there is no alternation of generations. 
176. The red alge (Class Rhodophycez), the largest 
and one of the most highly developed groups of seaweeds, 
are characterized by the presence of a red pigment called 
phycoerythrin,’ which very generally masks the chlorophyll 
completely. The carrageen already studied (page 112) belongs 
to this class. 
1 Mer’is-tem < Gr. meristos, divisible. 
2 Pa-raph’y-ses < Gr. para, besides; physis, growth. 
3 Phy’’co-er’y-thrin < Gr. erythros, red. 
