Sexual Organs of Phytophthora erythroseptica , Pethyb. 125 
incontrovertible as that at an earlier stage the oogonial incept was entirely 
within the antheridium. Both rest on observations which seem incapable 
of misinterpretation. In Fig. 4 are shown two transverse sections of the 
same antheridium. The oogonial incept is found in one (a) within the male 
organ, while in the other (b), which is through the upper part of the 
antheridium, it is seen that the oogonial incept has not yet penetrated so 
far. The same condition is shown in Fig. 3 in longitudinal section. 
There is strong positive evidence that the oogonial incept in a certain 
stage of its development is entirely within the antheridium. There is 
evidence of the same sort to show that it bursts through the upper 
antheridial wall and emerges freely at the top. And there is every reason 
to assume—and absolutely nothing to disprove—that the oogonial incept 
finds its way into the antheridium in the same way as it escapes from it later 
on, by piercing the lower wall. It is only necessary to follow the stages 
represented in Figs. 8 to 13 to be convinced that the organ which projects 
from the top of the antheridium develops into the oogonium. The develop¬ 
ment has been followed on living material by Pethybridge ( 27 ). The 
structure which we have called the oogonial incept, which pierces the 
antheridium and grows through it, emerges from its summit and forms 
the oogonium. 
It is convenient to have a word to express this position of the male 
organ in reference to the female, and we shall use the term ‘ amphigynous * 
for it. ‘ Hypogynous ’ and ‘ epigynous 5 are already in use to describe an the- 
ridia, and ‘ paragynous ’ might be suggested for such male organs as grow 
up to the side of the oogonium and pierce it there. 
It has been surmised by Pethybridge as a possible explanation of the 
penetration process that fertilization might take place while the oogonial 
incept was within the antheridium. This is not so. There is no union of 
the male and female elements at this time, the wall of the oogonial incept, 
in which there is no 'opening or rupture of any sort, keeping them apart. 
Whatever be the explanation of the penetration of the antheridium, 
it is not to be found in this. A normal act of fertilization takes place 
later on. 
The oogonia and antheridia are always borne on separate hyphae, as 
has been stated. The male organ may be terminal but is more often 
intercalary, and when it arises at, or very near, a point where the mycelium 
branches it appears to be borne on three hyphae. This is not at all 
infrequent, as might be expected in a richly branched mycelium. The 
most frequent condition is that shown in Figs. 7, c, and 16. The exact time 
at which it is cut off by a septum, or by septa, from the vegetative hyphae 
is not clear, and there appears to be considerable irregularity in this respect. 
Fairly late developmental stages are found in which septa are not yet 
formed. This possibly is an adaptation to relieve the pressure, which must 
