NEW SPECIES OF ACHLYA AND OF SAPROLEGNIA® 
A. J. PIETERS 
(WITH PLATE XXI) 
In the course of physiological work on Saprolegnia carried on 
during the past four years, there was occasion to make pure cultures 
of a large number of water molds. Altogether some 85 numbers 
were isolated and cultivated on flies or in artificial media or both. 
Among these forms were several that could not be induced to pro- 
duce oogonia and which could not, therefore, be referred to any 
species. The author is of the opinion that in some cases such forms 
have completely lost the power to produce oogonia and that they 
should be described and named as new species, the diagnoses to rest 
on physiological rather than on morphological bases. However, 
his experience with some of these forms shows that it will be well 
to be cautious in drawing conclusions. In the case of a variety of 
Saprolegnia monoica to be described, the form was in cultivation 
for 16 months, on flies and in various media, without any sign of 
oogonia being produced. Later, when just the right combination 
of conditions was presented, oogonia were produced. 
Another species, to be described as S. Kaufmanniana, produced 
oogonia sparingly on flies, many cultures not showing a single 
oogonium. In this form also a number of oogonia with oospores 
and antheridia were produced in a certain strength of haemoglobin 
solution, but in no other medium. These experiences show that 
the production of sexual organs may depend on some special com- 
bination of conditions, differing doubtless for each form. One 
form, which has been studied for 18 months as no. 66 and which 
has been tested in every way in which any of the other forms have 
been tested, still refuses to produce oogonia, though yielding an 
abundant harvest of round single gemmae. These gemmae have 
the shape and size of oogonia, and are commonly borne laterally on 
short stalks just as oogonia are in such a species as S. monoica. In 
* Contribution from the Botanical Laboratory of the University of Michigan, 
no. 148, 
483] [Botanical Gazette, vol. 60 
