On Fertilization in the Saprolegnieae. 
BY 
A. H. TROW. 
With Plates XXXIV-XXXVI. 
EN years ago, at the suggestion of Prof. Oltmanns of Freiburg, and 
X stimulated by the publication of Humphrey’s (’ 92 ) admirable mono- 
graph on the Saprolegniaceae of the United States, I commenced a study 
of the cytology of the sexual organs in the genus Saprolegnia . 
In the years 1894-5, as one of the results of a very long series of 
observations, the conclusion was reached that fertilization takes place 
invariably in Saprolegnia dioica and at least occasionally in S. mixta. The 
evidence, so far as it concerns the first of these two species, was excep- 
tionally simple, clear, and convincing, but it apparently proved unacceptable 
to a considerable number of botanists. The evidence rests on three distinct, 
and in the main, easily verifiable observations, viz. (1) the invariably 
uninucleate character of the oosphere-origins and oospheres, (2) the 
invariably binucleate character of the young oospores, and (3) the uninu- 
cleate character of the ripe oospores, a feature however which was not so 
definitely established as was obviously desirable. Special attention should 
be paid to this statement, for it has been recently suggested by Davis (’ 03 ) 
that my view as to the occurrence of fertilization in the Saprolegnieae 
rested on other and altogether insufficient grounds, viz. the occasional 
occurrence of binucleate oospheres (eggs). He says that I have found 
binucleate eggs (!) in Saprolegnia and ‘ attached much significance to them 
as evidence of sexuality.’ It is unfortunate that Davis uses the term eggs 
very loosely as synonymous with oospheres and oospores — indeed, as he 
does not figure the oospore membranes, it becomes difficult to ascertain 
whether he paid any attention at all to that critical period in development 
when the oosphere is converted into an oospore. I have seen, in S. dioica , 
on one or two occasions, binucleate oospheres and have of course regarded 
them as anomalies, even as monstrosities. Certainly, no theories were 
[Annals of Botany, Vol. XVIII. No. LXXII. October, 1904.] 
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