Godium dimorphum 



Annie May Hurd, 

 University of Washington, Seattle. 



Codium dimorphum and C. mucronatum are probably the only repre- 

 sentatives of the genus found in Puget Sound. C. dimorphum has been 

 reported from San Juan Island as C. adhaerens (10). As pointed out 

 by Svedelius (12) the two species differ in that the former is not tomen- 

 tose and is characterized by having two types of utricles. The presence 

 of trichomes is not mentioned in the original description of C. adhaerens 

 (1). Svedelius, however, in a letter to the writer, reports that as the 

 result of careful inquiry he has found that the original material of C. A. 

 Agardh (1) is identical with that of J. G. Agardh (2), who says that the 

 utricles are always tomentose and does not mention the presence of two 

 kinds of end walls on the utricles. The latter character and the absence 

 of trichomes is the basis for Svedelius' new species, C. dimorphum (12). 

 Comparison of a specimen of Svedelius' material with the Puget Sound 

 species showed that the two are identical. If Svedelius is justified for 

 the reasons given above in splitting a new species from C. adhaerens, we 

 must conclude that our species falls under C. dimorphum. 



C. dimorphum grows on rocks in the most exposed places in the lower 

 littoral zone. The less protected the habitat, the firmer and more vig- 

 orous are the plants. Individuals are often abundant on a single rock, 

 yet not found anywhere else in the locality, showing that this species is 

 not fitted for wide distribution. It was noticed that it was most fre- 

 quently found on the under side of overhanging ledges. Hauck (7) and 

 Falkenberg (6) have reported the same fact for C. adhaerens. Berthold 

 (3) found this, as well as other species of Codium, growing only in shaded 

 places, on the under side of overhanging rocks, or where the water was so 

 muddy as to protect the plants from direct sunlight. He says that the 

 effect of strong light is such that the plants tide over the summer and 

 reproduce only in winter and spring. Kiister (9). however, did not find 

 that Codium grew any more commonly or any differently in shaded places 

 than in brightly lighted ones. Other than that the plants were on the 

 under side of rocks more commonly than on the upper, no preference for 

 dimly lighted places was noted. 



The plant body consists of a dark-green flattened thallus, irregular in 



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