1901]  GAMETOGENESIS AND FERTILIZATION IN ALBUGO 163 
in A. candida. But certain peculiarities of the asexual organs 
make such a view improbable. The Albuginaceae and Perono- 
sporaceae may both have attained the uninucleate condition of 
oosphere independently, each being derived from ancestors 
having multinucleate oospheres. The probability of the multi- 
nucleate condition being the primitive one discredits the validity 
of Fischer’s position (1892, pp. 223, 224) regarding the deriva- 
tion of the Peronosporaceae and Saprolegniaceae from the 
Chytridiaceae. 
Oogenesis in the Saprolegniaceae resembles that in the 
Albuginaceae in having a multiplication of nuclei through a 
mitosis, followed by a degeneration of the superfluous nuclei, 
thus presenting very closely the condition seen in A. Trago- 
pogons. Trow, Hartog, and Humphrey (1892) failed to report 
a coenocentrum, but Dangeard (1890) has described a structure 
in both Saprolegnia and Peronospora which may prove to be the 
same (cf Wager 1896, pp. 308 and 322). 
From my own studies, Pythium closely resembles Albugo in 
its oogenesis. There is a withdrawal of the protoplasm from 
the oogonial wall, differentiating a vacuolate periplasm, clearly 
homologous with that of Albugo. Cytological knowledge of 
the events of oogenesis in this genus will have great value 
in determining whether its relationship is closest to the 
Peronosporaceae or Albuginaceae. The present indications 
favor the Peronosporaceae, where it was placed by DeBary 
(1881). 
Two diametrically opposed processes of oogenesis occur in 
the single-egged (eineiig) Albuginaceae and the many-egged 
(vieleiig) Saprolegniaceae. In the first there is a massing of 
protoplasm in the center, forming the rudimentary oosphere; in 
the second a peripheral accumulation of protoplasm leaves the 
central region comparatively free. There is in Peronospora, 
however, a movement toward the periphery rather than away 
from it, resembling in this respect Saprolegniaceae. It is con- 
ceivable that Pythium may represent a transitional condition 
between oogonia with single eggs and those with several, which 
