THE PLANTS OF THE SEA. 43 
Stockholm. The more recent studies of Derbes and Solier, and 
especially of Thuret and Pringsheim, have thrown the greatest 
light upon the propagation of marine vegetables. 
Red sea-weeds are propagated by two kinds of spores. The 
first kind, or ¢etraspores, bears long pods containing masses of 
four seeds or spores. These pods, or bulbs, carry within them- 
selves the means of germination. The spores properly so called 
are found in groups in proper conceptacles or folyspores. For 
their perfect development, the action of the aztheridia (transparent 
cells) seems necessary. In these cells granular bodies are moved 
about by means of vibratile hairs or czlza. These bodies are 
ZOOSPORES, 
true seeds. The antheridia pass through many different forms, 
and finally break up into numerous cellules. These cellules 
become detached ; they do not germinate, but it is probable that 
their action upon the polyspores is analogous to that which the 
green alge exhibit. It more frequently happens that each of 
these organs belongs to a distinct plant, so that the species com- 
prehends three individual forms, which is even more complicated 
than the fructification of the date palm, the male and female 
flowers of which bloom on separate trees. The green alge are 
chiefly propagated by zoosperms and by spores. The szoosperms, 
or zoospores, are minute microscopical corpuscles about 5,5,5th of 
an inch long, of an ovoid or top-shaped form, and two-thirds full 
of a green liquid called chlorophylle. One end of the minute 
body thins out to a point or beak, and out of this issue two 
or four threads longer than the whole corpuscles. In some of 
the alee these threads are unequal. The longer one is stretched 
out in front, while the other is trailed behind asa sort of rudder. 
Near the end of the beak is frequently seen a reddish spot, which 
remains some time after the germination has commenced, 
