Sexual Organs of Phytophthora erythroseptica , Peth-yb . 129 
a half. The cytoplasm is stratified in arcs of concentric circles, the centre 
of which would be somewhere in the stalk (Fig. 13). One has the impres¬ 
sion that it welled into the organ in waves or pulses, every wave being 
flattened out by the succeeding one and made visible by slight differences 
in density. The nuclei are still linear or bow-shaped, and they lie 
tangentially to the arcs of cytoplasm. Near the tip the stratification is 
no longer visible and the nuclei are becoming spherical (Fig. 13). About 
this stage' or a little earlier the oogonium is club-shaped, this being partly 
due to the fact that the rim of the antheridium acts as a retaining wall 
(Fig. 12). As the pressure increases this is overcome. The oogonium 
assumes a spherical shape, distending the rim of the male organ and 
rounding off its margin until it resembles the lip of a beaker. The normal 
shape of the antheridium is probably more or less spherical. After the 
oogonial incept has entered it, and before it emerges, the shape is altered 
almost to that of a cylinder with rounded ends (Fig. 5), obviously the 
result of the pressure exerted by the developing oogonium. When the 
oogonium has reached full size its pressure is exerted in the opposite 
direction, so that the antheridium now becomes stout and squat (Fig. 13). 
After the oogonium has emerged the wall of the antheridium thickens 
appreciably. When very young it may collapse if the cell be plasmolysed, 
but now it retains its shape under all conditions even though the proto¬ 
plasm may contract. So far as size and external appearances go the 
sexual organs are now mature. 
After the oogonium reaches its full size there is a progressive alteration 
in the physical appearance and the staining qualities of the cytoplasm, 
and this is one of the best means of arriving at the true sequence of events. 
In the beginning the cytoplasm was densely granular and almost homo¬ 
geneous, but it now gradually becomes more loosely vacuolate and less 
deeply staining. The number of nuclei which pass in is 90 to 100, 
more or less. At the time when the nuclei divide, however, there 
are only about thirty in the oogonium. It is evident that two-thirds of 
those originally present must either pass out again or degenerate. It is 
also possible that some nuclear fusions might occur, but there is no 
evidence whatever for a thing so unlikely, and the numbers, the average 
of a good many counts, do not support it. Neither is there any evidence 
that any nuclei go back into the parent hypha. After the oogonium 
reaches full size that hypha is practically empty, and it remains so. 
Besides, the oogonium is separated from it before the full reduction has 
taken place. On the other hand, all during the period prior to the 
division of the nuclei there are ample evidences of nuclear degeneration 
just as it has been described by Claussen (8) in Saprolegnia monoica and 
confirmed by Miicke ( 25 ) in Adilya. The most conspicuous degeneration 
figure is a deep-stained undifferentiated sphere, larger than a nucleolus 
K 
