ALGAE 107 



consist of an egg cell surrounded by a wall composed of five 

 spirally wound branches. The antheridium is a complicated 

 spherical structure with a wall of eight cells and containing a 

 large number of spermatozoids each provided with two flagellar. 

 No swarm spores are produced. 



245. Class 7. Phaeophyceae. — The Pha^ophyceai are the 

 brown sea weeds. Only a few small forms are found in fresh 

 water. Among the marine forms, however, are the largest of 

 all Cryptogams. Macrocystis pyrifera is said to attain a 

 length of over 200 feet. The plants are usually attached to 

 rocks by means of a hold-fast organ. No general statement 

 can be made concerning the form but in the larger species the 

 thallus is usually flattened and often forms broad sheets. The 

 cells are uninuclear and contain a number of chromatophores 

 which contain a brown pigment, phycophaein. 



246. Order i. — The Ph(Bosporece. reproduce asexually by means of swarm 

 spores produced in large numbers in "unilocular" sporangia. Sexual 

 reproduction occurs also through the conjugation of motile gametes 

 developed in multilocular sporangia (gametangia) one gamete being 

 developed from each cell of the sporangium. 



247. Order 2. — The Cyclosporece are farther advanced sexually. There 

 is a marked differentiation of egg and sperm. In one family, Dictyo- 

 taceae, asexual aplanospores are also produced but in the Fucaceae there is 

 no asexual reproduction. 



248. Class 8. Rhodophyceae.— The Rhodophyceae or Flor- 

 ideas are the red sea weeds. A few forms occur in fresh water. 

 The red sea weeds are small as compared with the brown. The 

 form of the thallus is most often a bushy mass of branching 

 delicate filaments or of thin sheets. Some species are encrusted 

 with calcium carbonate. The color is due to a red pigment, 

 phycoerythrin, found in the chromatophores in addition to the 

 green. Asexual reproduction takes place through non-motile 

 tetraspores, which are produced in groups of four on the surface 

 of the thallus. The sexual reproduction is peculiar. The male 



