HOW TO KNOW THE SEAWEEDS 



175b Cystocarps protruding above the surface of the blade. Fig. 220. 

 176 



Figure 220 



Fig. 220. Rhodymenia sp. 



A vertical section through a mature cystocarp to show its pro- 

 truding, dome-Uke, non-coronate form. The carpospores are produced 

 from a pedicellate gonimoblast. The ostiolar aperture is shown in 

 the top of the pericarp. 



Rhodymenia is a world wide genus of some three score species, 

 mostly red in color and found in lower intertidal or in infratidal habi- 

 tats. The cystocarps are very uriiform in structure, and, although 

 infrequently found in some species, are of great aid in identifying 

 the genus. Specific characters are mostly found in the vegetative 

 thallus and in the manner iii which the asexual reproductive spores 

 (tetraspores) are produced. The genus is much more richly developed 

 along the Pacific than the Atlantic Coast. Most of the North Ameri- 

 can species are illustrated in the writer's "Review of the genus Rhody- 

 menia with descriptions of new species." (A. Hancock Pacific Expedi- 

 tions 3:123-181. 1941.) 



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