Pieters : Ferax Group of Saprolegnia 
309 
having antheridia on about one half of the odgonia, 5". ferax 
scarcely ever producing antheridia, while the male organs are 
found on every oogonium of S. monoica. De Bary also calls 
attention to the fact that the hyphae of S', mixta are flaccid and 
delicate in appearance, while those of the other two species are 
stiff and strong. 
De Bary is very careful to make it clear that S. ferax is not 
wholly without antheridia (see ’8i, p. 92), and it is because this 
qualification on the part of de Bary has been sometimes over- 
looked that we find such statements as that by Kauffman (’08) 
that S. ferax “ is said to have no antheridia.” The formation of 
oogonia in the empty sporangium cases, thus forming the so-called 
“ cylindrical ” oogonia is also not given by de Bary as a character 
distinctive of 5'. ferax. There doubtless are forms in which this 
phenomenon occurs more often than in other forms, but the 
character is of no specific value. Humphrey says of 5". mixta, 
“antheridia . . . , absent from a part of the oogonia, sometimes 
from a large part.” 
My attention was first called to the question of what is S. mixta 
or S. ferax by Kauffman’s paper (’08) in which on page 368 he 
describes a form as S. mixta, though 75-90 per cent, of the 
oogonia were accompanied by antheridia, while on the following 
page he describes another form in which the male organs were 
found on only i or 2 per cent, of the oogonia. In experiments 
with the latter form, Kauffman was able to increase the number 
of antheridia to 25 per cent, of the oogonia but no more. A 
strict interpretation of the original description of S. mixta would 
exclude both of the forms with which Kauffman worked, as 
would also be the case with those the writer has collected and on 
which he found never less than 80 to 90 per cent, of antheridia. 
Kauffman considered that his form F. must be a form of S. mixta 
because he found antheridia, although he recognizes the differ- 
ence between his two forms and notes that the hyphae of his 
form “H.” are “rather slender” (p. 368). 
Klebs (’99) found that when he grew 6". mixta in a solution 
of haemoglobin, no antheridia were produced and this has also 
been the experience of the writer. On the other hand. Prof. W. 
C. Coker, of North Carolina, has stated in correspondence with 
