CLASS ARCHIMYCETES 29 



surrounds itself with a membrane, and discharges the naked protoplast 

 into the interior. This is carried to the tip of the hypha by the streaming 

 protoplasm and there separated from the host by a septum. It grows 

 rapidly at the expense of the host plant and after two days breaks up into 

 polyhedral portions (the young zoosporangia) each of which rounds off 

 and surrounds itself with a membrane. At maturity they form a short 

 papilla which pierces the host wall and allows the zoospores to escape. 



With falling temperature in stagnant water, resting conditions appear. 

 The individual sporangia are surrounded by a strong membrane, adapted 

 to resting over unfavorable conditions. A. Fischer calls them sporangio- 

 cysts. They are joined to a thick group (cystosorus) which is derived 

 as a whole from a single protoplast (Fig. 176). At germination the spo- 

 rangiocysts change into sporangia and, in a still unknown manner, dis- 

 charge the zoospores into the open. 





/S 



Fig. 18. — Rozella scptigcna. Part of host hypha with the false oogonia, each contain- 

 ing an echinulate hypnospore, d, containing the parasite; s, sporangium of the parasite. 

 (X 400; after Cornu.) 



Rozella septigena lives exclusively on Saprolegnia hyphae, (A. Fischer, 

 1882). As in Woronina polycystis, the parasite, after penetration, passes 

 with the streaming protoplasm to the apex where it divides repeatedly, 

 so that the daughter individuals are separated occasionally by the septa 

 of the host. Hence they lie behind one another in a row of single flabella 

 (Fig. 17c). After approximately two days, each changes to a sporangium 

 whose walls lie directly on that of the host hyphae. Thus a filament 

 infected by Rozella has the appearance of a hypha which has cut off several 

 gemmae. At germination the sporangium collects its protoplasm to a 

 thick covering on the walls, and cleaves into single zoospores which swarm 

 out through a papilla. The hypnospores arise in lateral outgrowths of 

 the single flabellum; their wall is closely echinulate (Fig. 18). Their 

 formation and germination are unknown. 



Belonging to the Woroninaceae or closely related to them is a series 

 of interesting forms whose life cycles are imperfectly known, as Pyrrho- 

 sorus marinus (Juel, 1901) and Pleolpidium inflatum (Butler, 1907). 



