312 
Mycologia 
the oogonia of ^S". ferax, and antheridia, usually of diclinous 
origin, were found on at least 90 per cent, of the oogonia. It is 
not impossible that single oogonia of S. mixta might be confused 
with those of S. diclina Humphrey, which has diclinous antheridia 
on round, poorly pitted oogonia, but the latter species, which I 
collected at Ann Arbor as number 38, has, as de Bary and 
Humphrey state, the oogonia mostly at the ends of long hyphae, 
rarely lateral and never racemose, while the lateral racemose 
arrangement is the rule in 6'. mixta. 
While it is probable that mistaken identifications may occur in 
the study of poor material of several of these species, the case 
is worst as between 5". ferax and S. mixta. If the almost com- 
plete absence of antheridia in the one case and their presence on 
one half of the oogonia in the other is decisive in these species, 
then neither of the two forms studied by Kauffman nor those 
discussed in this paper belong to 6". ferax or to S. mixta. At the 
same time, there is no doubt that such forms as my numbers 17 
and 82 are quite distinct from the others and that numbers 21F, 
25, 28, 33, 34, 35, and 37 all belong to the same species. The 
number of oogonia provided with antheridia may vary in the same 
form depending on the medium in which it is grown. As already 
stated, Klebs found that in 5". mixta the number varied from o 
to 90 per cent., Coker in correspondence, and Kauffman in the 
paper referred to have also recorded such a variation. In my 
study of the forms determined as belonging to 5'. ferax, I found 
that oogonia-bearing antheridia were much more common on the 
parts of the mycelium near the body of the fly than on the outer 
portions of the mycelium, and also that the antheridia were much 
more easily seen when the culture was young than after it had 
grown rather old. Under the influence of low temperature, there 
were generally more antheridia than when the culture was kept at 
room temperature, about 22 degrees Cent. Saprolegnia monoica 
is said to have antheridia of androgynous origin on every 
oogonium, but when I grew this in 0.05 per cent, haemoglobin 
solution, the number of antheridia present varied from o to 17 
per cent, of the number of oogonia. When a mycelium that had 
previously been grown in pea extract, was transferred to o.oi per 
cent, haemoglobin plus M/200 levulose, the oogonia were small. 
