1925] SetcheU-Gardner: Mclanophyrecu 477 



very closely to a typical Myrionema, but the multiseriate gametangia 

 represent a stage in developmenl which we have not admitted into 

 that genus. The gametangia occupy a definite zone on the outer ends 

 of the erect filaments. Practically all of the erect filaments bear 

 gametangia. 



At times the basal layer seems to be distromatic, or even poly- 

 stromatic, but careful investigation shows that this appearance is 

 occasioned by the overlapping creeping filaments whieh follow the 

 v< ry irregular surface of the host, due to the death of its surface 

 layer of cells, probably before the epiphyte took possession. The 

 zoosporangia are very sparse, but specimens have been seen which show 

 undoubted zoospores. 



5. Compsonema pusillum 8. and G. 



Plate 54, fig. 3 



Fronds forming thin, light brown cushions, irregular in outline, 

 3-4 mm. diam. ; prostrate portion composed of very tortuous, branched 

 filaments following closely the irregularities of the host, producing a 

 few filaments from the under side penetrating among the cells of the 

 host ; erect filaments simple, cylindrical, 270-300/t long ; cells of creep- 

 ing filaments very irregular in shape and size ; cells of erect filaments 

 cylindrical, 6-7/* diam., 3-5 times as long; chromatophore a slightly 

 broken band ; true hairs absent ; zoosporangia spherical to ovoid, sessile 

 or on short pedicels on the creeping filaments, 18-25/j. (up to 40/0 

 long, 16-22//. broad; gametangia cylindrico-conical to blunt fusiform, 

 sessile or on short pedicels on the creeping filaments, 40-60/* long, 

 10-12/* broad ; loculi 1-2-seriate. 



Growing on the pneumatocysts of Ncrcocystis Luetkeana. Carmel 



l 



Bay, Monterey County, California. 



Setchell and Gardner, Phyc. Cont. Ill, 1922, p. 356, pi. 37, fig. 3. 



Compsonema pusillum seems to overlap each of several genera. Its 

 zoosporangia, gametangia, and penetrating filaments ally it with 

 Streblonema. Sauvageau (1897) has figured a Myrionema with 

 rhizoids. The gametangia are very small and have about as many 

 uniseriate as biseriate loculi. It might be considered a very minute 

 creeping Ectocarpus. We have placed it with the genus Compsonema 

 on account of the scarcity of fruit in proportion to the sterile tissue, 

 and on account of the monostromatic base, believing that the penetrat- 

 ing filaments are more or less accidental on account of the injured 

 condition of the surface layer of cells of the host. 



