LEPTOMITALES 867 



thirty or thirty-five nuclei migrate into the developing oogonium before 

 it is separated from its hypha by a cross wall (Fig. 68 A, p. 866). In the 

 mature oogonium all save one of the nuclei are arranged around the 

 periphery (Fig. 68 B). No single large central vacuole is formed, as is 

 characteristic of the sporangium, but, rather, several large irregularly 

 disposed ones appear. 



Each of the nuclei has a fairly prominent dark-stained nucleolus and 

 several dark-stained peripheral granules. Differentiation of the content 

 of the oogonium then ensues. The peripheral material forms numerous 

 polygonal vacuoles, whereas the inner, main content develops a fairly 

 regular meshwork of smaller vacuoles. The supernumerary nuclei are 

 arranged in the protoplasmic meshwork in a thin vacuolate layer of 

 periplasm or between the periplasm and the ooplasm, and the single 

 oogonial nucleus is in approximately the center of the somewhat denser 

 ooplasm (Fig. 68 C, p. 866). There follows an almost simultaneous 

 mitotic division of all the nuclei (Fig. 68 D). The spindles produced 

 during this process have no definite orientation and are intranuclear. 

 After division the periplasm in which the now paired smaller super- 

 numerary nuclei lie becomes more deeply stained. Evidences of nuclear 

 degeneration are apparent. One of the two central nuclei becomes the 

 egg nucleus; the other, like the periplasmic nuclei, degenerates. 



The antheridium, the broad apex of which is applied near the base 



ooplasm is completed. D. Nuclear division in oogonium; the three visible 

 nuclei of antheridium have not as yet divided. E. Oogonium, showing a 

 single central beaked egg nucleus with a centrosome from which radiate 

 striae; resorption of periplasm is in progress and strongly stained inclusions 

 have made their appearance around periphery of egg; first indications of wall 

 formation are visible; antheridium has produced fertilization tube, its nuclei 

 have divided, and one gamete nucleus has just entered base of tube; deep- 

 staining material at tip of tube indicates that deliquescence of apex has begun. 

 F. Oogonium in which male nucleus is shown approaching larger egg nucleus; 

 degeneration of supernumerary nuclei and resorption of periplasm is in progress; 

 dark-staining peripheral material is clearly defined, as is wall. G. Egg with large, 

 nearly like-sized, paired male and female nuclei; oospore wall has taken on 

 its typical contour; periplasm has for most part been resorbed, though 

 occasional periplasmic nuclei still persist, as does fertilization tube. H. Mature 

 oospore; nuclei have not as yet fused. 

 (Behrens, 1931) 



