A Contribution to the Physiology of the Saproleg- 
niaceae, with special reference to the variations 
of the sexual organs . 1 
BY 
C. H. KAUFFMAN. 
University of Michigan. 
With Plate XXIII. 
T HE Saprolegniaceae have been a favourite subject for investigation by 
some of the most prominent botanists of the last century. Unger 
(’43), Schleiden (’42), and Naegeli (’47) were among the first contributors 
towards a knowledge of these fungi, while Pringsheim (’57, ’60, and ’74) 
and De Bary (’81) gave them the first extended morphological and 
systematic study. In 1872 Cornu began a monograph which he never 
finished. De Bary gave them special attention up to the last years of his 
life, and his accurate observations and experiments were reported post- 
humously in 1888 by Solms-Laubach. In this country Humphrey (’93) 
extended our knowledge of American forms and summed up the taxonomic 
facts in a monograph. In more recent years investigations have taken 
new directions: Trow (’95, ’99 and ’04), Hartog (’95 and ’99), and Davis 
(’04) have attacked the problems of fertilization and of nuclear phenomena 
by means of modern cytological technique, while Klebs (’99 and ’00) has 
obtained important experimental results towards a theory of reproduction. 
It is upon the foundation laid by Klebs that the present investigation 
has attempted to build ; and the following paragraph may be considered as 
presenting the lines along which advance seemed possible : — 
(a) The method which Klebs applied to the study of a single species 
has been used for a comparative study of a number of species of the same 
genus. ( b ) The special problem of sex determination or at least of 
antheridial development has been approached with a species whose repro- 
ductive organs are more suitable for such study than those of Saprolegnia 
mixta. (< c ) An effort has been made to learn something of the taxonomic 
values of those characters which have been generally used in the genus 
1 Contribution ninety-three from the Botanical Laboratory of the University of Michigan. 
[Annals of Botany, Vol. XXII. No. LXXXVII. July, 1908. J 
