THE FERAX GROUP OF THE GENUS 
SAPROLEGNIA^ 
A. J. Pieters 
(With Plate 170, Containing 2 Figures) 
Nees von Esenbeck (’23) first separated the then known forms 
of water molds into two genera, Achlya and Saprolegnia, but, 
until the time of de Bary’s first paper (’52) in 1852, this dis- 
tinction was not recognized by subsequent workers ; de Bary 
revived the classification of the older author. Meanwhile all 
forms of water molds had been called Saprolengia ferax or 
Achlya prolifera, without any clear distinction being made be- 
tween these genera. In 1850, Thuret (’50) described the swarm 
spores of a form that he called S. ferax Kiitz., and he figured, 
for the first time, the oogonia. Later de Bary (’81) referred to 
this figure when he renamed 5 ". ferax, S. Thureti. 
In 1857 Pringsheim (57) contributed to the literature the de- 
scription of 5 ". monoica with excellent figures ; other forms of 
Saprolegnia, those without antheridial branches, he considered as 
belonging to 5 . ferax. In 1873 he stated that further observa- 
tion had convinced him that there was no true specific distinc- 
tion between the forms with an antheridium on every oogonium 
and those in which the antheridia are almost or quite wanting. 
They differ, he says, “ only in the relative number of antheridia.” 
He therefore grouped all forms of Saprolegnia with round, pitted, 
many spored oogonia into the "ferax" group. 
In 1881, there appeared a paper by de Bary (’81) in which he 
united 5 ". monoica, S. torulosa, and 5 ". Thureti {S. ferax) into 
a group which he called the ferax group. He had not yet dis- 
tinguished 6". mixta. In his description of i". monoica, de Bary 
followed Pringsheim, but added that in some cases the antheridial 
branches arise from hyphae remote from the oogonium, or, in 
other words, are not androgynous. 
1 Contribution from the Botanical Laboratory of the Univ. of Mich. No. 147. 
307 
