CHYTRIDIALES 159 



like forms found by him in marine algae in Denmark. Some of these 

 have upon later investigation (Sparrow, 1934c, 1936b) been found to 

 possess biflagellate zoospores and have been referred either to Peter- 

 senia or to Olpidiopsis. Further work may establish the fact that the 

 remainder of these marine fungi should be segregated from Pleotrachelus. 



A spherical thick-walled resting spore which produces zoospores 

 upon germination has been figured by Morini (1913) in Pleotrachelus 

 zopfianus, but further observations are needed to confirm the oc- 

 currence of such resting structures in the genus. 



Future critical examination of all olpidioid fungi will no doubt 

 result in the suppression of Zopf 's genus, but it does not seem desir- 

 able to do this here. The peculiar lateral attachment of the flagellum 

 of the zoospore in P. wildemani is also known in Olpidiomorpha (see 

 p. 122). Its significance is not as yet clear. Recent work seems to in- 

 dicate that in some chytrids flagellar attachment may often be subapical. 



KEY TO THE SPECIES OF PLEOTRACHELUS 



Sporangia predominantly spherical 



In Pilobohts 



Typical sporangia bearing numerous discharge tubes 



P. FULGENS, p. 159 



Typical sporangia bearing from one to two discharge tubes 



P. zopfianus, p. 160 



In rhizoids of mosses P. wildemani, p. 160 



Sporangia broadly oblong-cylindrical; in green algae 



P. PETERSENII, p. 161 



Pleotrachelus fulgens Zopf 



Nova Acta Acad. Leop.-Carol., 47: 173, pi. 16, figs. 25-36. 1884; Beitr. 

 Physiol. Morph. niederer Organismen, 2: 7, pi. 1, figs. 11-14, pi. 2, figs. 



1-5, 7-8. 1892 



(Fig. 12 E, p. 124) 



Sporangia from one to eighty in the host, causing a marked spherical, 

 pyriform, or broadly fusiform swelling of the infected parts, exactly 

 spherical, 6.5-250 u, in diameter, with a colorless or light-yellow or 

 red to reddish-brown fairly stout cellulose wall and from one to th irty 



