218 SOME NOVA SCOTIAN* AQUATIC FUNGI. MOORE. 



B. Fungi with -a mycelium of delicate thread-like hyphse, 

 mostly saprophytic, rarely parasitic, living in water or 

 facultatively in moist air ; zoosporangia generally spheri- 

 cal, resembling in form the oogonia and strongly marked 

 oft from the vegetative portions of the hyphse ; formation 

 of oospores preceded by a sexual act ; conidia present. 



3. Pythiac <'((>. 



The zoospores are produced in sporangia and are formed in 

 large numbers by the simultaneous division of the contents of 

 these organs, and, as has been stated, usually escape as swarm 

 spores. In all of the genera of the family Saprolegniaceoe, with 

 the exception of Pythiopsis, Dictyuchus, Thraustotheca and 

 Aplanes, the swarm spores escape as terminally biciliate 

 zoospores, and soon after their escape encyst. After a period 

 of rest, generally a few hours, they escape from their enclosing 

 membranes and pass through a second swarming stage as more 

 or less kidney shaped later-ally biciliate zoospores. After a 

 second encystment germination takes place. This phenomenon 

 is referred to as diplanetisni. In Pkytkiopsis. the second 

 swarming stage is suppressed and germination takes place im- 

 mediately upon the escaping zoospores first coming to rest. In 

 Dictyuckics, the zoospores encyst within the sporangia and 

 finally escape, each by a separate opening through the outer 

 wall, and then appear with lateral cilia. In this genus the first 

 swarming stage is suppressed. The same suppression is also 

 found in Thraustotheca, and in the genus Aplanes the disappear- 

 ance of the swarming stages is practically complete. Here the 

 spores germinate within the sporangium, the germ tubes push- 

 ing out through the wall. 



The history of the swarm spores in the family Leptomitacece 

 has not been so completely worked out, but in the genera 

 Leptomitus and Apodacfdya, they appear to be diplanetic. 



In the third family of the order, Phthiacece, the swarm 

 spores are monoplanetic. 



