THE ALGiE 



235 



kinds are the most beautiful of all the marine species. The 

 colors of red algse 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 

 Algae. — Sexual reproduction 

 among these algae 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 Fig. 165. BatracJwspermum, a 



a hair-like extension on which ^<=<^ ^^ea. (Slightly magni- 



the sperms become lodged. 



Asexual reproduction is frequently accomplished by the 



formation of spores produced 

 in fours and known as tetra- 

 spores (Fig. 168, B). 



303. Additional Notes on the 

 Algae. — The algse embrace 

 so many types of plant life, in- 

 cluding in aU 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 



Fig. 166. Part of a Filament 

 of Batrachospermum, not the 

 species 'of Fig. 165. (Highly- 

 magnified.) 



