SS eee a 
ail 
1901} GAMETOGENESIS AND FERTILIZATION IN ALBUGO 79 
I wish to express my chief thanks to Professor Strasburger 
for daily counsel during the progress of this research; to Pro- 
fessor Magnus for names and synonymy; to my wife for the 
preparation of the slides, and for Plate IV; and to the Univer- 
sity of Chicago for the advantages derived from a traveling fel- 
lowship. 
lx DESCRIPTIVE. 
ALBUGO PORTULACAE. 
The early stages of the sex organs in A. Portulacae differ in 
no essential detail from those described for A. Buti (Stevens 
1899, figs. 42, 43, 45, 59-65). The nuclei are distorted as the 
protoplasm flows into the developing oogonium, but’ as this 
structure attains its full growth and recovers its turgor they 
regain their spherical form and enlarge, rapidly assuming the 
spirem condition. They are more numerous than in any of the 
other species examined, ranging from 300 to 400 in each oogo- 
nium, and are smaller than in A. Bit, rendering this an unfavor- 
able type for cytological study. 
The aggregation of the cytoplasm into several regions of 
greater density is the first indication of the development of the 
oosphere (jfig.z). The aggregations soon coalesce, forming one 
large mass of fine uniform cytoplasm. Apart from the struc- 
tural differences between the dense alveolar center and the 
vacuolate filar periphery, there is a very distinct difference in 
stain reaction. The dense fine-grained cytoplasm refuses the 
gentian, but takes the orange G lightly, while the vacuolate 
peripheral cytoplasm takes the gentian strongly. The uniform 
dense alveolar region is the rudimentary oosphere, and is cen- 
trally placed in the oogonium (jig. 3). 
Throughout this differentiating process the nuclei, which are 
now in mitosis, are crowded out of the denser masses and come 
to lie near the larger vacuoles (fig. 2). Therefore, after the 
denser masses have coalesced and the larger vacuoles are forced 
into the periplasm, the nuclei are to be found near the rather 
indefinite boundary between periplasm and ooplasm. This 
boundary, however, becomes distinct and sharp immediately 
. 
