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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.