OMYOCETES 



85 



In their youngest fundaments, the antheridia and oogonia agree with 

 those of other Peronosporacese. They arise as terminal swellings of 

 hyphal branches, whereby the antheridia acquire about 35 nuclei, the 

 oogonia up to 300. At the spot where the antheridium is attached to the 

 oogonium, the oogonial and antheridial walls are digested by an enzyme; as 

 possibly the osmotic pressure of the oogonium is higher than that of the 

 antheridium, the oogonial content, surrounded by a membrane, bulges 

 like a papilla into the antheridium. This papilla is unfortunately 

 named a receptive papilla. Later this is turned back and is followed by 

 the fertilization tube which penetrates the pore. 



In the oogonia the nuclei are regularly scattered throughout the 

 protoplasm. During their simultaneous division a fundamental 



Fig. 52. — Albugo Bliti. Development of oospores. 1. Antheridium and oogonium. 

 2. Mitoses at the periphery of oosphere. 3, 4. Penetration of copulation tube. 5, 6. 

 Copulation figures of male and female nuclei. 7. Mature oospore. {After Stevens, 1899.) 



rearrangement occurs in the whole oogonium. Most of the protoplasm 

 draws together into the dense oosphere, while the periplasm remains 

 spongy and much vacuolate; then the nuclei are extruded from the 

 oosphere and deposited in the periplasm. 



The details of development in the various species of Albugo differ 

 considerably from each other. In Albugo Bliti (Stevens, 1899) and A. 

 Portulacce (Stevens, 1901), a marked border layerae forms between the 

 periplasm and oosphere. A part of the nuclear spindles are so placed 

 (Fig. 52, 2) that only one daughter nucleus lies in the periplasm the 

 other in the oosphere; in this manner 40 to 50 nuclei return to the oosphere. 

 Here they soon divide for a second time (Fig. 52, 4), while those of the 

 periplasm remain resting. Meanwhile the protoplasm in the center of 

 the oosphere has become condensed into a small deeply staining 

 coenocentrum, which appears to attract the nucleus. Its signifi- 



