HOW TO KNOW THE SEAWEEDS 

 170a Species of Atlantic Coast occurrence. Fig. 212. .Chondrus crispus 



Fig. 212. Chondrus ciispus 

 (Linnaeus) Stackhouse 



A portion of a plant re- 

 moved from a clump, X 0.8. 

 Although this species may not 

 readily be distinguished from 

 the Pacific Rhodoglossum af- 

 fine except through the study 

 of certain reproductive details, 

 the two need not be confused, 

 for their ranges on opposite 

 coasts do not overlap. C. cris- 

 pus occurs from New Jersey 

 northward and is the famous 

 Irish Moss which has been 

 collected commercially for over a century, especially around Scituate, 

 Massachusetts. It is the source of a phycocolloid called carrageenin 

 which is widely used as a stabihzer in chocolate milk, salad dressings, 

 tooth paste, lotions, syrups, etc. About a milUon pounds are produced 

 in a year. 



Figure 212 



170b Species of Pacific Coast occurrence. Fig. 213 



Hhodogiossum affine 



Figure 21 3 



Fig. 213. 

 KyUn 



Rhodoglossum afiine (Harvey) 



A portion of a plant removed from 

 a clump, X 0.8. This is the only dicho- 

 tomous member of Rhodoglossum in 

 our territory. It is widespread along 

 the coast from central Oregon south- 

 ward. In central and southern Cah- 

 fornixt it is often dominant in some in- 

 tertidal, rocky shore areas. It is ex- 

 ceedingly variable in width of thallus 

 parts, in color, and in branch shape, so 

 that many specimens which may be 

 found will not appear to agree with the 

 illustration. The more or less clearly evident dichotomous branching, 

 the filamentous structure and smooth surfaces of the segments will dis- 

 tinguish it. 



161 



