138 Murphy.—The Morphology and Cytology of the 
is worthy of note that the nuclei are not distributed throughout the peri¬ 
plasm as they are in Peronospora. Such an absorption has been described 
by many authors in the case of Pythium and to a less extent in that of 
Phytophthora. The matter is dealt with more fully in the discussion at 
the end of the paper. 
At the time when the periplasm is disappearing the fertilization tube 1 
begins to be pushed in (Figs. 24, 25#, and 26). The tube is not produced 
in this Fungus until the oosphere is almost ready for fertilization ; in striking 
contrast to the procedure in Albugo , where it may be formed while the 
nuclei are still in prophase, and in contrast to that in most other Perono- 
sporales to a less extent. It is another link in the long chain connecting 
Phytophthora and Pythium however (Miyake, 24 ). It seems probable 
that it is actually pushed in. The turgor of the oogonium has now fallen 
so low that it is exceptional to find one which is not contracted a little 
somewhere, while the antheridium never contracts at this time. The 
pushing in of the tube and the act of fertilization take place while the 
periplasm is being absorbed by the oosphere. It would be impossible to 
say that one regularly precedes or succeeds the other, which is also a point 
of resemblance to Pythium and to Nozemia Fagi (Hartig, 19 ). Consequent 
on its functioning very soon after formation the tube is exceedingly difficult 
to find while still containing a nucleus (compare Miyake, 24 ). This is 
aggravated by its small size—as a rule it does not penetrate farther than 
is shown in Fig. 25, a , though cases were observed where it reached nearly 
to the centre. Sometimes, however, it is even shorter than this, as shown 
in Fig. 26, and as the position of the male nucleus testifies, which often 
lies in contact with the spore wall near the antheridium. Further, it stains 
very lightly and all attempts to stain it more clearly were failures. As 
a consequence only a comparatively few examples were found although 
a large amount of time was spent examining material of about the right 
age. It was considered, however, that the cases already found demonstrated 
the point clearly enough and that further expenditure of time would not 
be justified. The contracted and very hyaline remains of the tube are 
quite commonly found after fertilization is accomplished, lying as a rule 
in the now empty oogonium or running out towards the developing 
oospore (Fig. 28). It was in this way that the structure was first found. 
The discarded tube proves one thing which is not always clear otherwise 
(see Fig. 26)—that there actually is a tube and not merely an opening 
between the two organs. The tube-like nature and the opening to the 
antheridium can often be made out in the empty condition. 
1 It might be suggested that this structure is not really homologous with the fertilization tube 
of other Oomycetes since it is part of the oogonium. It is, however, quite comparable to the tube 
in species of Pythium with ‘ stalk ’ antheridia, which is always called by the same name. Further, 
it has never been shown in the case of paragynous antheridia whether one organ or both form the 
tube, and if one, which. 
