SAPROLEGNIALES 819 



Coker and Matthews (1937: 59) describe this type of spore discharge 

 as Dictyuchus-Yike. The characterization seems hardly accurate, however, 

 since in Eurychasma the secondary zoospores never penetrate the spo- 

 rangium wall, but emerge through the orifice. 



IMPERFECTLY KNOWN SPECIES OF EURYCHASMA 



? Eurychasma sacculus H. E. Petersen 



Oversigt Kgl. Danske Vidensk. Selskabs. Forhandl., 1905 (5): 477, 



fig. VIII, 5, 8-9 



Sporangium irregularly saccate, epibiotic part 48-184 \x long, with 

 two short discharge tubes, endobiotic part 40-192 \x long, contorted 

 and lobed, constricted where it passes through the superficial layer of 

 host cells ; other characters unknown. 



In Halosaccion ramentaceum, coll. A. Jessen, Rhodymenia palmata, 

 coll. H. P. Sorensen, Greenland. 



Found most frequently in host cells beneath the superficial layer, 

 rarely in the central cells. 



Petersen (conversation, 1933) does not regard the species as distinct 

 from Eurychasma dicksonii. If the lobed nature of the endobiotic part 

 of E. sacculus is not due to the action of preservatives, however, this 

 character as well as the nature of the host plants (Rhodophyceae) may 

 separate it from the inhabitant of phaeophyceans. 



Formation of papillae by fungus during vacuolate stage. /. Extrusion of 

 fungus from host cell by bursting of confining wall of latter; more distal 

 portion of host wall may be seen between the two papillae. K. Two infected 

 host cells; fungus to the left has burst host wall. L. Sporangium in which 

 zoospores have been formed before extrusion from host cell; papillae were 

 present but were not seen in this view. M. Extruded sporangium showing 

 single broad papillae and, within, peripheral layer of zoospores. N. A "net 

 sporangium" ; all but two zoospores have evacuated their cysts; walls of latter 

 appear as network of polygonal cells. O. Two dwarf sporangia. P. Zoospores 

 being discharged from sporangium; no evidence of previous encystment of 

 these spores could be observed. Q. Zoospores killed with 1 per cent osmic 

 acid and stained with fuchsin. R. Portion of "net sporangium" showing partial 

 emergence of zoospore from its cyst. 5. Sporangium with two open discharge 

 tubes, showing peripheral layer of spores. 

 (Sparrow, 1934c) 



