1896, ] Aquatic Fung. 321 
spores are biciliate, much flattened, bean-shaped, with a 
slight indentation on one side, near which the cilia are at- 
tépresents the same coarsely granular structure. € z00- 
spores are monoplanetic and in R. Americanum only the first 
stages of germination have beenobserved. The figures given 
inthe Traité de Botanique® illustrate their further develop- 
ment in R. znterruptum, and indicate that the body of the 
toospore itself gives rise directly to the expanded portion of 
the basal cell, the hypha of germination forming the stalk and 
Producing the rhizoids from its apex. The spore thus devel- 
ops as it were upside down. 
: The oogonia are formed like the sporangia, but are usually, 
if not invariably terminal, and are similarly distinguished from 
the filaments which bear them by the characteristic constric- 
tion. They are almost perfectly spherical in form and con- 
‘ain a single large oosphere which is not readily distinguish- 
able from the rather abundant peripheral protoplasm unt 
ater fertilization has been accomplished. The antheridial 
lament in the American species, which, unlike the two 
European forms, is androgynous, arises immediately below 
the insertion of the oogonium; and is usually very short and 
slender (figs. 13 and 14), seldom, if ever, exceeding the length 
presented in fig. 12, The antheridium is rather small 
wall of which it per- 
brates without indentation. The two European forms differ 
Not only fro re heterogynous, but on ac- 
. y trom the fact that they a se che atheridial 
. « 
= In the Traité de Botanique (fig 617, Ia), may ier 
“med to be at the base, as in R. Americanum, in accor 
Tr 
_rraité de Botani 
Cos que 1024. fig. 617. 2. 
4, Monograph 28. 
