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 oogonium, of 

 the genus Albugo 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 oosphere of A. filtti and A. portulacece (Stevens, 

 '99, '01) is paralleled among plants only by Pyronema (see p. Hi) 

 and the possible case of Sporodinia 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. bliti, A. portulacece 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 ('01), 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 consequently 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 



