229 
Species of Olpidiopsis , (Cor mi) Fischer . 
d-g , as they appear soon after the two protoplasms have become fused ; 
b , c, and //, in the fusion stage ; #, large nuclei from the section represented 
in Fig. 47. 
Unfortunately, no later stages of the oospores of this species were 
observed in section. In the other species, however, an interesting arrange- 
ment of the contents of the mature oospores takes place. Fig. 46 shows 
a portion of a section of an almost mature oospore of O. luxurious. The 
content is more or less differentiated into zones which show different 
staining reactions, especially with the triple stain. The outer zone is made 
up of fine granular protoplasm in which are embedded a large number of 
faintly staining nuclei. Inside of this is a zone of less definite outline com- 
posed of larger granules which stain rather deeply with gentian violet. The 
outer zone retains more of the safranin. In or near the centre is a large oil 
globule which stains with orange G. 
Fig. 45 shows a section of a mature oospore. The same zonate 
character of the contents is evident. Fig. 90 is a photomicrograph of the 
same section. When iron-alum haematoxylin is used on such material the 
zonate character is less distinct and the nuclei can rarely be seen at all 
(Fig. 89). 
The endospore becomes very much thickened in the mature oospore, 
while the hyaline spine-bearing exospore remains unchanged. The former 
stains slightly with orange G and eosin, the latter usually remains hyaline. 
In sections of O. vexans oospores there is only an occasional indication of 
a roughened or warty condition of the exospore, which would point to 
the assumption that such markings were due to some encrustation which 
dissolved in the preparation of the material. 
There is no contraction of the oogonial protoplasm to form an oosphere 
and no apparent changes comparable to those taking place in oogenesis in 
the higher Oomycetes. After fertilization the oogonium becomes the 
oospore directly. 
D. Nuclear Division. 
The nuclei of both sporangia and gametes are small, measuring in the 
resting stage 4-5 /x in diameter. In the early stages of development of the 
sporangia, and up to the time of fertilization in the sexual spores, they have 
a rather strong affinity for stains, especially in division stages. The nucleoli 
and chromatin masses take on a brilliant red colour with safranin, while the 
spindle fibres stain very faintly with gentian violet. All material fixed in 
Flemming’s solution proved much less satisfactory than that fixed with 
medium chrom-acetic acid for nuclear divisions. 
The resting nucleus (Figs. 49 and 50) possesses a deeply staining, 
rather prominent nucleolus and a slightly granular nuclear plasm. A rather 
indistinct network with frequent deeply stained thickenings, which I take to 
