254 BOTANICAL GAZETTE [OCTOBER 
the seeking of the female by a male. The number of anther- 
idial nuclei which migrate into the oosphere bears no constant 
relation to the number of waiting female nuclei. The failure of 
some nuclei to leave is probably due to a lack of irritability. 
Superfluous nuclei of either sex which cannot resume vege- 
tative function degenerate. 
The periplasm has the ability to form the pectiniferous 
deposit, but the differentiated ooplasm cannot.. Emanations 
from the antheridial tube seem to be needed to stimulate the 
ooplasm to this activity. The pectiniferous layer is deposited 
on or by a plasmoderma or tonoplast. 
The four species, A. Portulacae, A. Bliti, A. Tragopogonts, and 
A.candida constitute a series in which the coenocentrum increases 
in complexity, the receptive papilla decreases, and the number 
of functional nuclei decreases. Of these A. Portulacae is prob- 
ably the most primitive, and A. candida the most highly special- 
ized form. 
The coenocentrum was an important factor in evolution from 
the multinucleate to the uninucleate condition of oosphere. 
The division of the fusion nucleus before passing to the 
winter condition is a consequence of the uninucleate condition, 
and constitutes the initial step in germination. 
Delay in the division of the fusion nucleus in a uninucleate 
oospore is associated with retarded and slow fusion of the sexual 
nuclei, and is explicable as a consequence of slowness in com- 
pletion of the last steps of fusion. 
The relation between Albugo, Peronospora, and Saprolegnia 
is emphasized by their cytological character, and all are probably 
derived from a common ancestor having a multinucleate oosphere. 
The derivation of Peronospora and Saprolegnia from the Chy- 
tridineae is rendered improbable. 
Pythium is more closely related to the Albuginaceae than to 
the Saprolegniaceae. 
The peripheral gathering of the protoplasm in the oogonium 
of Saprolegnia may indicate closer relation to Peronospora than 
to Albugo. 
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