1896.] Aquatic Fungi. 327 
The new species above alluded to may be characterized as 
follows: 
Rhipidium americanum, nov. sp.—Plate XXI, figs. 1-15. 
Basal cell very variable in form and size, attached by copi- 
ous thizoids; above more or less regularly one or more times 
successively dichotomously branched or lobed, the lobes or 
tanches erect or spreading in a radiate fashion, the upper or 
external edges giving rise to numerous filaments from which 
they are distinguished by the characteristic constrictions. The 
filaments continuous or less frequently consisting of two or 
three sub-clavate segments. Sporangia typically ovoid taper- 
ing from the broad base to the bluntly rounded apex, but 
varying greatly in form, erect, originally terminal, one to four 
Succeeding one another on a single filament; rarely two or 
three borne together terminally. Oogonia terminal, spherical, 
the thick-walled oospore colorless, the exospore elevated in a 
Series of anastomosing ridges which give the spore an irregu- 
larly stellate outline. Antheridial filaments short, slender, 
arising immediately beneath the oogonium from the same 
segment; the antheridium small, rounded, applied close to the 
base of the oogonium. Basal cell 75 to 400¢ long. Fila- 
Ments 50 to 800 long, seldom longer. Sporangia 30X20 to 
0x27, average 50x35". Oogonia 40-554. Oospores 
30-454 in diameter. d 
: arious decaying vegetable substances in ponds an 
poe, vicinity of Cambridge, Mass., and of Kittery Point, 
aine, 
e late spring 
and were it 
iy Observed the occurrence of more tha 
‘angium. Such forms are also muc 
