Io8 MYCOLOGY 



plasm occurs in Albugo blitl and .1. portulacce and the oosphere is 

 multinucleate and the' nuclei present fuse in pairs with a number of 

 sperm nuclei which enter from the antheridium. The oospore which 

 arises is multinucleate. This method is considered by mycologists to 

 be the primitive one as displayed in these two species, the uninucleate 

 oospheres of the first-named species having been derived from the multi- 

 nucleate. An intermediate position is occupied by Albugo tragopogonis, 

 where at first the oosphere is multinucleate but by the degeneration of 

 all but one female nucleus becomes uninucleate. Claussen^ finds that 

 Sa'prolegnia monoica develops both antheridia and oogonia, the latter 

 at first being filled with protoplasm and many nuclei which wander to 

 the periphery and undergo degeneration with a few nuclei left over. 

 These nuclei divide once mitotically. Around these daughter nuclei 

 the protoplasm collects to form the egg cells. Each egg has a single 

 nucleus near which is the coenocentrum of Davis, but which Claussen 

 thinks is a true centrosome. The simple or branched antheridia form 

 germ tubes which enter the wall of the oogonium and a single male 

 nucleus fuses with the nuclei of the egg cells to form the oospore. 

 Claussen contrasts the life cycle, as determined by his investigations, 

 with those of Trow in the following diagrammatic presentation: 



Trow Diploid Haploid Diploid 



/ Antheridium — Male nucleus \ 



/ \ 



Oospore, Mycelium Oospore 



Multinucleate \ / 



\Oogonium — Egg cell — Egg nucleus/^ 



Claussen Haploid Diploid. 



Strasburger considers that the superfluous nuclei in the oogonia and 

 the antheridia are comparable with the superfluous egg nuclei of certain 

 of the brown seaweeds belonging to the family Fucace^. When the 

 oospores germinate, they either produce directly a mycelium, or give 

 rise to zoospores. The fungi of this order are essentially parasitic, 

 being found in this condition as endophytic parasites, or as endozoic 

 parasites on fishes and insects and Euglena. 



1 Claussen, P.: Ueber Eintwicklung und Befructung bei Saprolegnia monoica. 

 Festschrift der Deutsch. Bot. Gesellsch., xxvi; 144-161 with 2 plates, 1908. 



