1913] Blanchard,— Two new Species of Stigonema 197 
the fact that in many of the branches the cells are no longer than those 
of the main filament or are shorter; in its secondary branching, and 
in its branching not being distinctly unilateral. 
The genera Hapalosiphon, Stigonema, and Fischerella are in many 
respects alike. In the table on the next page their chief characteristics 
may be compared at a glance. "This table gives a little more latitude 
than some of the best writers allow; O. Kirchner, for instance, does 
not admit secondary branching in Hapalosiphon. Different accounts 
of the same species in these genera often vary greatly, but a safe 
ground has been taken in compiling this table. 
It will be seen from this summary that these genera are separated 
from each other by no clear and definite lines. There are several 
intergrading forms. "The characters that are used to distinguish them 
are as follows: 
Hapalosiphon grows free-floating in fresh water. 
Fischerella grows in moist earth, on wet stones, and in hot springs. 
Stigonema grows free-floating or on wet stones. 
Stigonema 1s usually much wider than either of the other two; is 
often composed of several rows of cells, and the cells are usually more 
rounded than in Hapalosiphon. 
The branches in Fischerella come from a creeping main filament and 
are unilateral. In Hapalosiphon, the branching is unilateral and sec- 
ondary branching is relatively uncommon, while in Stigonema the fila- 
ments may be repeatedly branched in every direction. In contrast to 
Stigonema, Hapalosiphon has the cells of its branches longer than 
those of the main filament. A brown or black sheath is character- 
istic of Stigonema, but some of its species have a colorless sheath. 
The question now is whether these differences are sufficient to sepa- 
rate three genera, especially after considering the characteristics of 
the two new plants above described. Bornet and Flahault in “ Revi- 
sion des Nostocacées Hétérocystées," 1887, class those forms now 
known as Stigonema under the subgenus Szrostphon, and treat Fischer- 
ella as another subgenus of the genus Stigonema. Later, 1895, Gomont 
proposed raising Fischerella to the rank of genus, basing his proposal 
“sur la différenciation trés marquée des filaments primaires rampants, 
relativement aux filaments dressés.” West, in “ British Fresh Water 
Algae” considers Fischerella to belong with Hapalosiphon. 
Thus, there has already been considerable difference of opinion as 
to the relationship of these forms. Stigonema anomalum shows simi- 
