FUNGI : SA PROLEGNIA . 



127 



after this process has taken place. Sometimes the slender antheridium can 

 be seen coiled partly around the oogonium, and one end entering to come in 

 contact with the egg cell. But in some species the antheridium is not 

 present, and that is the case with the species figured at 135. In this case 



B 



Fig. 141. Fig. 142. 



Gonidiophores and gonidia of potato blight (Phytophthora in- Gonidia of potato 



festans). />, an older stage showing how the branch enlarges where blight forming zoogo- 



it grows beyond the older gonidium. (After de Bary.) nidia. v After de Bary.) 



the eggs mature without fertilization. This maturity of the egg without 

 fertilization is called parthenogenesis, which occurs in other plants also, but 

 is a rather rare phenomenon. 



284. In fig. 136 is shown the oogonium and an antheridium, and the 

 antheridium is carrying in the male nucleus to the egg cell. Spermatozoids 



Fig. 143- 



Fertilization in Peronospora alsinearum ; tube from antheridium carrying in the sperm 

 nucleus in figure at the left, female nucleus near ; fusion of the two nuclei shown in the two 

 other figures. (After Berlese.) 



are not developed here, but a nucleus in the antheridium reaches the egg 

 cell. It sinks in the protoplasm of the egg, comes in contact with the nu- 

 cleus of the egg, and fuses witji )t, Thus fertilization is accomplished. 



