68 



THE LOWER FUNGI— PHYCOMYCETES 



3. Rozella Cornii (1872: 114). 



A small genus containing two species, one R. septigena Cornu 

 (Fig. 8) parasitic in threads of Saprolegnia, the other, R. simulans 

 Fischer, in Achlija. After the entrance of the infecting swarm- 

 spore the parasite exists for a time as a naked protoplast indis- 

 tinguishable from the protoplasm of the host. It grows at the 

 expense of the host, and finally fills entirely the lumen of 

 the host hypha. The formation of transverse septa divides the 

 thallus into a single row of short cylindrical sporangia whose 



Fig. 7.- — (a-d) Olpidiop.sis vcxans Barrett, {c) O. saprolegniae Cornii. (a) 

 Swollen tip of hypha of Saprolegnia containing both emptied and unemptied 

 swarmsporangia of the parasite, (h) Single sporangium with abnormal, long, 

 coiled exit tubes, (c) Biciliate swarmspores. (d) Emptied swarmsporangia 

 and verrucosa resting spores with companion cells, (c) Spiny resting spore with 

 companion cell. (After Barrett 1912.) 



lateral walls are fused with the wall of the host. Each spor- 

 angium breaks up into a large number of biciliate swarmspores, 

 and these escape through a short, usually lateral exit papilla. 

 Other thalli assume the spherical form and develop into thick- 

 walled spiny resting spores lying free in the host cell. They occur 

 more often in short lateral branches which tend to become globose, 

 and have in young stages the aspect of immature oogonia. The 

 method of germination of the resting spore is unknown. No 

 evidence of the existence of sexuality in the genus has been 

 encountered. 



