ALBUGO (CYSTOPUS). 



97 



structure seem not unlike those of higher plants. The number of 

 nuclei in the young oogonium, at this stage, varies with its size, the 

 average being from 70 to no. The antheridium, containing from 6 



D 



FIG. 35. Development of sexual organs and fecundation in Albugo (Cystopus) Candida. (After Wager.) 



A, antheridium attached to wall of oogonium, just beginning to push out its conjugating tube; dense 



mass of cytoplasm and several nuclei seen near projection. 



B, young oogonium after its delimination from mycelium, with antheridium attached ; receptive papilla 



projects from oogonium toward antheridium ; nuclei seem to be entering prophase of division. 



C, later stage ; protoplasm has contracted into a large central mass ; nearly all the nuclei have divided, 



and are collecting at periphery of central mass ; the deeply stained mass of cytoplasm, a (central body, 

 ccenocentrum), is seen in center in contact with egg-nucleus; egg-nucleus is derived from one of the 

 original nuclei of oogonium. 



D, oogonium into which conjugating tube has penetrated ; differentiation of periplasm and ooplasm 



becoming apparent, though a plasma membrane has not been formed around the egg ; in center of 

 ooplasm is the egg-nucleus near the dense mass of cytoplasm; in end of conjugating-tube is dense 

 cytoplasm in which lies the male nucleus. 



E, later stage than D ; apical wall of conjugating tube, becoming very thin ; plasma membrane of egg 



not yet formed. 



to 12 nuclei, now applies itself to the oogonium. The structure 

 both of its nuclei and cytoplasm is similar to that of the oogonium. 

 Soon after the two organs come into contact with each other, a portion 



