OOMYCETES 



33» 



Schenk) ; or different individuals produce the oogones and the 

 antherids (Lagenidium, Ancylistes). A perforation having been made 

 in the oogonial wall, the whole of the protoplasm of the antherid empties 

 itself into the oogone (there being no periplasm), and the united mass 

 rounds itself off and becomes the oosperm. The germination of the 

 oosperm has not been observed. 



Propagation takes place by means of zoospores (Lagenidium), and 

 to this end either the whole thallus-hypha becomes transformed into a. 

 zoosporange, or it is divided into a series of such. Each zoosporange 

 sends out through the membrane of the host-cell to the surrounding 

 water a protuberance, through which the contents escape after the 

 fashion of Pythium, forming uniciliated zoospores, which ultimately 

 attack the fresh cells of other algae. In Ancylistes the only propagation 

 known is a process of extension of its hyphse from one host to another. 



Literature. 



Cornu — Monogr. des Saprolegn. {loc. cit.). 



Cornu— Note sur I'oospore du Myzocytium proliferum, Schenk (Bull. Soc. Bot> 



France, xvi. , 1869, p. 222). 

 Pfitzer— Ein neuer Algen Parasit (Monatsber. Berl. Acad., 1872). 

 Schenk — Ueber das Vorkommen contractiler Zellen im Pflanzenreich (Wiirzburg, 1858). 

 Zopf — Ueber einen neuen parasitischen Phycomyceten, &c. (Lagenidium) (Bot. Zeit.^ 



1879. P- 35I). 



Order 3. — Monoblepharide^. 



The single genus 

 Monoblepharis (Corn.), 

 like the preceding 

 group, is , closely re- 

 lated to Peronosporese 

 and especially to Py- 

 thium. The thallus- 

 hyphse bear both ter- 

 minal and interstitial 

 oogones, in which there 

 is no preliminary dif- 

 ferentiation of peri- 

 plasm, but the whole 

 protoplasm contracts 

 and forms the 00- 

 sphere, while the apex 

 of the oogonial wall opens. The antherid (usually a cell adjoining an 

 oogone) produces several swarming antherozoids, which escape, one of 



Fig. 290. — Monoblepharis sphariccc Cornu. 

 oogone, 0^ and antherid, a., antherozold, ^. 

 successive stages ( X 800). (After Cornu.) 



Filament bearing an 

 The numbers indicate 



