146 Murphy .— The Morphology and Cytology of the 
firmatory. He shows periplasmic nuclei in mitosis (?) after the delimitation 
of the oosphere which are practically devoid of all cytoplasm. There 
can be little doubt that Rosenberg was mistaken in supposing that the 
oogonial nuclei divide a second time. It is common to find elongated 
and otherwise distorted nuclei at this stage in P. erythroseptica also, which 
at first sight simulate division stages, but which certainly are not. The 
author has also seen spindles in poor material (particularly in a lot of 
slides which were stained with Gram’s stain) which exactly resemble the 
spindles Rosenberg (and Stevens also) considers typical of the second 
division, yet it can be stated positively that there is only one division 
in this Fungus. Rut whether there be one or more mitoses in Plasmopara 
one can see that after division the superfluous nuclei are extruded and 
all the protoplasm ultimately finds its way into the oosphere, just as it 
does in Phytophthora . 
It is clear that Pythium , Phytophthora , Sclerospora , and Plasmopara 
are closely related in the organization of their ooplasm and periplasm. 
They agree also, both among themselves and with Peronospora , in having 
no coenocentrum comparable to the granular mass in Albugo Candida , in 
the delayed fusion of the sexual nuclei, and in division of the fusion 
nucleus being so retarded that they all (probably) rest in a uninucleate 
condition. Morphological and biological evidence suggests strongly that 
these genera including Peronospora , form a natural group, and it would 
require strong cytological evidence to prove the contrary. Peronospora 
must be derived from a form like Plasmopara or Albugo. Morphological 
considerations undoubtedly point to Plasmopara ; the cytological seem 
to point in both directions. If the classification be based mainly on 
cytology there seems to be a fairly close relationship between Albugo 
Candida and Peronospora , but if particular emphasis be laid on morphology 
the difference between them is wide. On the other hand, the morphological 
and biological evidence that Pythium and Peronospora are closely con¬ 
nected is so perfect that the conflicting deductions arrived at from cyto¬ 
logical study must be interpreted as supporting the biological and other 
evidence that connects Peronospora with the other genera which at present 
make up the Peronosporaceae. The consequence of this is that the 
Albuginaceae are placed apart from all the other forms, and that the 
remaining genera of the Peronosporales fit into a gradually ascending 
series in somewhat the following order: Pythium , Phytophthora , Sclero¬ 
spora, Plasmopara , and Peronospora. Those forms only are included the 
cytology of which has been worked out. It is evident from a consideration 
of this series that the periplasm is an increasing structure (in this particular 
case at all events), that is, if one takes a full view of the series and compares 
Pythium or Phytophthora with Peronospora . It is less easy to be sure 
from a consideration of other investigators’ accounts and figures, particularly 
