178 SEAWEEDS 
flora of the warm and temperate Atlantic and Medi- 
terranean. Characium, a genus of about thirty spe- 
cies, of which only two are marine, is a stalked form 
with ovate cells, and Codiolum and Sykidion more or 
less resemble it vegetatively. 
The Reproductive Organs.—Chlorochytrium  pos- 
sesses gametes which escape from the mother-cell 
embedded in a mucilaginous mass, and conjugate 
Fic. 55.—Halosphera viridis. a, showing the protoplasm gathered round 
the nuclei and lining the wall; b, the outer membrane, cast off after enlarze- 
nent of the sphere, the daughter-cells separated from the wall ; ¢, d, e, s 
in the development of zoospores; at e, the hour-glass shape is preliminary 
to division into two ; f, zvospore highly magnified. (After Schmitz). ‘ 
before leaving it. The zygote remains motile by 
means of the four cilia (of the two  bi-ciliated 
gametes), and eventually on coming to rest 
surrounds itself with a membrane, and pene- 
trates the tissue of the host-plant by means of 
a short germ-tube. C. dermatocolu.r, which inhabits 
Polysiphonia and Sphacelaria, and C. taclusum, which 
