308 
Mycologia 
Pringsheim had maintained that if one starts with a form 
having antheridia and continues the culture for some time, the 
number of antheridial branches gradually decreases in successive 
cultures until finally one may have forms without any antheridia. 
De Bary, however, showed that in his work each form, when 
secured in a pure culture, maintained its distinctive antheridial 
characters unchanged and suggested that impure cultures ex- 
plained Pringsheim’s results. Among the members of his 
“ ferax” group de Bary distinguished S. torulosa by the arrange- 
ment of the oogonia in chains, S. Thureti {S. ferax) by the single 
large round oogonia, almost none of which have antheridia, and 
5. monoica by the constant presence of androgynous antheridia. 
At this time, de Bary did not yet recognize 5". mixta, nor did he 
include 5". hypogyna Pringsheim in the ferax group, although this 
species had been described by Pringsheim in 1873 as a variety of 
5". ferax. In 1888, however, in de Bary’s last paper (’88), pub- 
lished after his death, he included in the "ferax” group S. 
Thureti, S. hypogyna, S. monoica, S. mixta, S. torulosa, S. dioica 
(S. diclina of Hurhphrey), and 5". anisospora. Pringsheim had 
previously included in the ferax group all those forms having 
smooth, round, pitted, many-spored odgonia, differing only in the 
number of oogonia accompanied by antheridia. De Bary seems 
to have departed from the historical conception of the "ferax” 
group and added to it such forms as 5'. anisospora with unpitted 
oogonium wall, eccentric oospores and zoospores of two sizes. 
I prefer to follow Humphrey (’92) who limits the "ferax” 
group to 5". ferax, S. mixta, and S. monoica, and these are 
undoubtedly the forms included under this term by Pringsheim, 
although he did not recognize S. mixta as being distinct from 
S. ferax. 
If we turn to the original descriptions to ascertain the limits 
of the species, we find that in all cases the oogonia are described 
as round, smooth, and pitted and with a varying number of 
oospores. De Bary, indeed, states that the oogonia of 6". Thureti 
{ferax) are generaly larger than those of monoica, but as be- 
tween mixta and ferax no distinction based on the oogonia is 
made. The specific difference, as de Bary plainly states, lies in 
the number of oogonia accompanied by antheridia, 5". mixta 
