NO. 10 DAWSON : MARINE ALGAE, GULF OF CALIFORNIA 235 



This peculiar brown alga may be distinguished from all others on our 

 coast by its dichotomous, complanate fronds, 4-7 cm. high, composed of a 

 medullary tissue of tangled hyphal cells and a cortex of rows of anti- 

 clinally arranged cubical cells. 



As to the systematic position of the plant Segawa says : "Ishige Yendo 

 was put by Yendo under the Fucaceae in his 'Fucaceae of Japan,' but re- 

 cently zoospores have been observed by different authors and the new 

 family has consequently been established. 



"Of the establishment of the new family Okamura is of the opinion 

 that Ishige may be put in the Chnoosporaceae, though Chnoospora has a 

 parenchymatous structure in the inner layer instead of a filamentous one. 

 Apart from this difference of structure of the frond, uniseriate gametangia 

 alone are known in Chnoospora, while in Ishige, zoosporangia only. So, 

 until the true nature of both kinds of reproductive organs of both genera 

 is fully known, it certainly seems best, at present, to place Ishige in a 

 family of its own." 



Ishige foliacea Okam. was separated from /. Okamurai Yendo by 

 Okamura. It had been considered by Yendo a foliose type of the more or 

 less cylindrical /. Okamurai. These plants were first described from 

 Japan and are known to be common on the warmer coasts of that country 

 as well as along the coast of China, to Amoy and southward. Up to the 

 present record it has not been known outside of Far Eastern habitats. 



On the coast of Japan and China both foliose Ishige foliacea and the 

 more or less cylindrical Ishige Okamurai grow together in the same locali- 

 ties. In the Gulf of California, on the other hand, only the former has 

 been found. The Gulf plants are identical in structure and in external 

 morphology with Japanese plants of /. foliacea, and the summer collec- 

 tions show in some sections cortical cell rows which seem to bear zoospo- 

 rangia as figured by Okamura (1936, fig. 131). Fronds vary in width 

 from 1 to 5 mm., the narrowest ones being found in July, the broad ones 

 in Februaiy. 



This plant seems to be perennially abundant on many reefs and rock- 

 shingle beaches of the upper half of the Gulf. In winter it was found 

 plentiful in the middle littoral zone at all of the shore stations visited be- 

 tween San Esteban Island and Tepoca Bay. In summer it competes with 

 Dictyota Johnstonii as the most conspicuous rock cover on the south shore 

 of Tiburon Island. 



D. 190, Puerto Refugio, Jan.; D. 313, Gonzaga Bay, Jan.; D. 388, 

 Tepoca Bay, Feb. ; D. 446, San Esteban Island, Feb. ; D. 680, south shore 

 of Tiburon Island, July. 



