468 University of California Puhlications in Botany [Vol. 8 



it in the genus Myi'ionema. because of the preponderance in number 

 of uniseriate loculi and monostromatic filaments in the prostrate 

 portion. 



16. Mjrrionema attenuatum S. and G. 



Plate 55, figs. 6, 7 



Fronds forming microscopic, more or less confluent strata on the 

 surface of the host ; prostrate portion composed of regularly radiating 

 filaments; erect filaments unbranched, attenuated gradually upwards 

 and at the base, 180-220/x long ; true hairs absent ; cells of creeping 

 filaments, 4.5-5. 5/a diam., nearly quadrate; cells of erect filaments 6-7 [x 

 diam., variable in length ; zoosporangia unknown ; gametangia sparse, 

 cylindrical to slightly fusiform, on shorter or longer pedicels, 30-45fi 

 long, 4.5-6|U, broad. 



Growing on the stipes of Macrocystis pyrifera, Laminaria Farlowii, 

 and on the sterile base of Gigartina radula f. Carmel Bay, Monterey 

 County, California. 



Setchell and Gardner, Phyc. Cont. II, 1922, p. 34<1, pi. 34, figs. 6, 7. 



It seems that sterilization has proceeded in this species of 

 Myrionema until about two-thirds of the erect filaments no longer 

 produce gametangia, and these filaments are several times longer than 

 the gametangia. The cells are slightly doliiform in some collections. 



17. Myrionema attenuatum f. doliiforme S. and G. (Orthog. mut.) 



Plate 55, figs. 4, 5 



Fronds forming small, irregular tufts among other epiphytic algae ; 

 erect filaments up to 275/a long ; cells of erect filaments quadrate to 

 3 times as long as broad, decidedly doliiform ; gametangia occasion- 

 ally small and terminal on the long erect filaments, otherwise as the 

 species. 



Growing on the stipe of Macrocystis pyrifera. Carmel Bay, 

 Monterey County, California. 



Myrionema attenuatum f. doUiformum Setchell. and Gardner, Phyc. 

 Cont. II, 1922, p. 344, pi. 34, figs. 4, 5. 



The chief distinction between this form and the species, 31. 

 attenuatum, is the decided doliiform character of the erect filaments. 

 Small terminal gametangia appear very frequently on the long, erect, 

 filaments. 



