70 University of Calif ornia Piihlicatians in Botany [Vol.8 



appearance of a very delicate net, although many short filaments crawl 

 out into the interstices. 



In the specimen collected, Phormidium hormoides is mixed with 

 another undetermined filamentous species of Myxophj^ceae, about 0.8/* 

 diam., with cylindrical cells longer than the diameter and with con- 

 spicuous cross walls. 



Ph. hormoides has some re&emblance to the young filaments of a 

 very delicate species of Anahaena on account of the pronounced moni- 

 liform trichomes, but there is no indication of heterocysts or spores. 



Section 2. Euphormidia Gomont 



Trichomes rarely or scarcely torulose, straight or curved at the 

 apices, in many species capitate. 



Gomont, Monogr. des. Oscill., 1892, p. 159 (1893, p. 179, Repr.). 



3. Ph. amhiguum Gomont 



4. Ph. lucidum (Ag.) Kuetz. 



5. Ph. suhmenibrmiaceum (Ard. and 



Straff. ) Gomont 



3. Phormidium ambiguum Gomont 



Stratum more or less expanded, dark or yellowish green or at times 

 aeruginous, filaments long and flexuous ; sheath either firm or mucous 

 and diflSuent, somewhat thick and lamellate; trichomes aeruginous, 

 slightly constricted at the dissepiments, 4-6/i, diam. ; cells one-fourth 

 the diameter long, occasionally granular at the cross walls ; apices 

 neither attenuate nor capitate ; terminal membrane slightl}" thickened. 



Growing on wood and on stones in the upper littoral belt. Bridge 

 across an estuary to Bay Farm Island, Alameda, California, Septem- 

 ber, 1903. 



Gomont, Monogr. des Oscill., 1892, p. 178, pi. 5, fig. 10 (1893, 

 p. 198, Repr.). 



We are inclined to refer to Phormidium amhiguum a specimen 

 collected in Alameda, California, which forms a distinct dark green 

 layer, with sheaths fairly thick, firm and distinct, but only slightly, 

 if at all, stratified. The cells are very short (only 1.5/a at times) and 

 there are no granules on the dissepiments. The apical cell is rounded 

 or even, at times, almost conical, with a very slightly thickened mem- 

 brane. 



