THE ALGE 235 
kinds are the most beautiful of all the marine pects: The 
colors of red alge vary in dif- 
ferent genera all the way from 
bright red to dark purple or 
reddish brown ; one fresh-water 
genus, Batrachospermum (Figs. 
165, 166), is often greenish. 
302. Reproduction in Red 
Alge.— Sexual reproduction 
among these alge is highly com- 
plicated. It may be briefly 
described as due to the action 
of peculiar non-motile sperms 
upon the egg contained in a 
flask-shaped cell provided with 
a hair-like extension on which 
the sperms become lodged. 
Fic. 165. Batrachospermum, a 
Red Alga. (Slightly magni- 
fied.) ? 
Asexual reproduction is frequently accomplished by the 
Fic. 166. Part of a Filament 
of Batrachospermum, not the 
species of Fig. 165. (Highly 
magnified.) 
formation of spores produced 
in fours and known as tetra- 
spores (Fig. 168, B). 
303. Additional Notes on the 
Alge.— The alge embrace 
so many types of plant life, in- 
cluding in all at least twelve 
thousand species, that it is not 
easy to make general state- 
ments which will apply to all 
the groups. The number of 
species may be more easily 
understood when it is mentioned that. a single genus of 
diatoms contains some nine hundred species, and a genus 
