528 University of California Puhlications in Botany [yo-L. 8 



Myelopliycus intestinale presents a different aspect when young 

 from that of the older plant. This is seen particularly at the tips 

 which are long acuminate when young, but blunter and often worn 

 away in age. The younger plants seem less conspicuously^ twisted than 

 the older. Our plant has fewer layers of cells in the intermediate 

 layer and shorter cortical filaments than the M. caespitosum of Japan. 



Myelophycus intestinale f. tenue S. and G. 



Plate 40, fig. 50 



Fronds densely caespitose, inconspicuously twisted, 1.5-2.5 cm. 

 high, 0.25-0.75 mm. diam. ; zoosporangia broadly ellipsoidal, 40-45/x 

 long, 30-35/A broad. 



Growing on rocks, usually in shaded localities, and where the spray 

 dashes against the rocks, along high-tide level. Coos Bay, Oregon, to 

 central California. 



"Myelophycus intestinalis f. tenuis" Setchell and Gardner, in 

 Gardner, New Pac. Coast Mar. Alg. I, 1917, p. 385. 



FAMILY 9. STRIAEIACEAE kjellm. . 



Fronds filiform, solid, more or less branched, trichothallic, mono- 

 siphonous at first, later usually of two sets of tissues, the inner of 

 larger, colorless, more or less elongated cells, the outer a single layer 

 of medium sized cells placed in horizontal rows and having chromato- 

 phores; unilocular zoosporangia and plurilocular gametangia super- 

 ficial or projecting beyond the surface in sori of more or less definite 

 circumscription and usually in transverse rows; with or without 

 paraphyses, 



Kjellman, Handbok I, 1890, p. 53. 



It seems best to follow Kjellman and keep the seemingly very 

 distinct genera, Stictyo siphon, Striaria and their near relatives 

 separate from the Asperococcaceae and the Scytosiphonaceae and 

 retain them among the Striariaceae. Both the gametophytes and the 

 sporophytes are known and are similarly macroscopic, but conditions 

 are otherwise in the other two families just mentioned. In the 

 Asperococcaceae there are dissimilarities in size, at least in some 

 species, between the individuals bearing gametangia and those bear- 

 ing zoosporangia, although neither is properly microscopic so far as 

 known. Among the Scytosiphonaceae, only the gametangial form is 

 known, suggesting that the zoosporangial form may be heteromorphic. 



