Sexual Organs of Phytophthora ery th rosep tic a , Pethyb. 141 
material, as is certainly (3), the secondary endospore, a thick layer which 
stains brown with orange G. Compare Pethybridge ( 1 . c.), where he shows 
that it is dissolved prior to germination. 
There is no deposit of the nature of an exospore laid down outside the 
primitive wall. This, correlated with the absence of periplasm after 
fertilization, explains the smoothness of the spore in the species, as indeed 
probably in the whole genus and in Pythium (to a less extent) and 
Saprolegnia. So far as the writer knows the oospores are always 
irregularly marked in the Albuginaceae and Peronosporaceae, that is, in 
families in which the periplasm is known to persist. The mature oospores 
are spherical, smooth-walled bodies, the wall being about two microns or 
a little more in thickness. If they happen to be formed in a confined space 
they adapt themselves to the form of their surroundings. It not infrequently 
happens that the oogonium, after it has grown through the antheridium and 
become spherical, puts forth a club-shaped outgrowth. The nuclei which 
pass into this divide and go into zonation normally, the oosphere and 
oospore which result retaining the abnormal shape of the organ which 
contains them. 
All during the formation of the spore wall the two sexual nuclei 
remain apart. If the male was originally in contact with the wall it 
remains there and may be seen even flattened out against it (Fig. 31). 
Both nuclei grow considerably in size. They now show a distinct nucleolus 
and chromatin masses, and rarely a trace of linin network. When the wall 
is nearly mature they begin to approach and finally come into contact, the 
fusion taking place in a leisurely fashion judging by the number of cases 
found (Figs. 32, 33, and 34). The part of the membrane separating the two 
nuclei disappears and the contents begin to mingle. Eight-shaped figures 
representing this condition are not very uncommon, and in the next stage 
is found a rather elongate nucleus of a large size without any constriction. 
Finally an oval or spherical resting nucleus results. The last stages in 
particular are difficult to stain well on account of the accumulation of coarse 
oil globules in the cytoplasm and around the nucleus. Early in the 
formation of the spore one sees these oil drops being formed, very small at 
first and then increasing in size (one can see them coalescing) and number. 
At first they seem to be of a solid substance, for they persist in the fixed 
material. Later these disappear, and instead one finds occupying much 
more than the greater part of the spore a large empty space, which con¬ 
tained oil in the living condition. The cytoplasm becomes more and 
more gathered into clumps with increasing spaces between. Finally it 
occupies a relatively small area of the spore; most of it is distributed 
around the wall in a thin layer, but there are a few aggregations of larger 
size, in one of which the nucleus lies (Fig. 35). The oospore rests in the 
uninucleate condition, but its further cytology has not yet been worked out. 
