96 FECUNDATION ; HETEROGAMETES. 
more distinctly granular. It contains also a rather large and distinct 
nucleolus. When the two nuclei come in contact, the male is smaller 
than the female (Fig. 34, E). Fusion now takes place (Fig. 34, F, G), 
and the fusion-nucleus presents at first a fine hollow framework in 
which lie numerous chromatin granules of about equal size; later it 
becomes smaller and denser, appearing more finely granular, when 
finally a large nucleolar body is again present (Fig. 34, H). 
ALBUGO (CYSTOPUS). 
The nuclear behavior and certain cytoplasmic phenomena manifested 
in the development of the sexual organs, especially the odégonium, of 
the genus A/éugo is, so far as known, unique among the Thallophyta, 
if not in the plant kingdom. The union of several male with several 
female nuclei in the odsphere of A. d/¢t¢ and A. portulacee (Stevens, 
’99, ’01) is paralleled among plants only by Pyronema (see p. 111) 
and the possible case of Sforodinta grandis. We shall confine our- 
selves first to the development of the sexual organs and fecundation in 
Albugo candida, referring in a later paragraph to the phenomena 
described for A. d2¢t2, A. portulacee and other-closely related repre- 
sentatives of the group. 
The following statements are based largely upon the researches of 
Wager (’96), probably the most complete account published for this 
species. The observations of Wager have been confirmed by the later 
studies of Berlese (’98), Davis (1900) and Stevens (’o1), those of Davis 
and Stevens presenting more clearly certain details regarding the 
central body of differentiated cytoplasm in the oogonium. The more 
obvious details in the development of the sexual organs are too well 
known to bear repetition, and cgnsequently the reader’s knowledge of 
that part of the process is assumed. 
The antheridium, which appears almost simultaneously with the 
oogonium, is more or less densely filled with granular cytoplasm in 
which several nuclei are present when the partition wall is formed 
delimiting the antheridium from the parent hypha. Previously to 
or during the early development of the conjugation-tube, the nuclei 
undergo a karyokinetic division by which their number is doubled 
(Fig. 35, A). 
When a quantity of cytoplasm and numerous nuclei have passed 
into the enlarging primordium of the oogonium, a transverse wall is 
formed separating it from the parent hypha. The cytoplasm shows a 
foam structure, and the nuclei are more or less regularly spaced in its 
reticulum (Fig. 35, B). The nuclei possess a membrane, and in 
