20 



THE SIMPLE HOLOCARPIC BIFLAGELLATE PHYCOMYCETES 



that the method of cleavage is fundamentally dif- 

 ferent in the Saprolegniaceae but primarily centri- 

 fugal in direction, because of the presence of a large 

 central vacuole which displaces the protoplasm in a 

 comparatively thin layer at the periphery. Doubt- 

 less when cleavage in Eurychasma and Ectrogella 

 has been intensively studied from fixed and stained 

 material the fundamental similarity of the process 

 will become quite evident. 



The secondary zoospores emerge from the cysts 

 after a short dormant period (figs. 15, 20, 27). In 

 E. Gomphonematis the numerous small granules 

 present in the primary swarmers fuse during the en- 

 cysted stage and form a single large refractive glob- 

 ule. These zoospores are oval and pyriform in shape 

 with two unequal flagella inserted laterally or close 

 to the anterior end. In motion the shorter flagelluni 

 is directed forward, while the longer one is dragged 

 along behind (figs. 16, 21). Unlike those of the uni- 

 flagellate rhizidiaceous chytrids the zoospores swim 

 more evenly and do not dart about in a zigzag path. 



Resting spores have so far been observed only in 

 E. perforans (fig. 35) and E. Licmophorae (figs. 33, 

 34). In the former species no sexual fusion has been 

 reported and the spores appear to be nothing more 

 than spherical, thick-walled, encysted thalli or spo- 

 rangia. In the latter species, however, Scherffel fig- 

 ured a thick-walled spore lying in a thin envelope 

 with a hyaline thin-walled, empty vesicle or com- 

 panion cell attached to one side by a broad tube (fig. 

 34). He regarded the resting spore as a oospore in 

 a rudimentary oogonium which has been formed by 

 fusion of the protoplasts of an antheridium and egg 

 cell through a broad conjugation canal. Scherffel 

 did not observe actual fusion in E. Licmophorae, 

 and figure 34 may relate to nothing more than an 

 irregular thallus, the content of which contracted 

 into a thick-walled resting spore in the larger of the 

 two lobes, as is suggested by figure 33. Resting spore 

 formation of this type is not uncommon in species of 

 the lower simple fungi, i.e., Olpidium gregarium, 

 Cantenaria Anguillulae, etc. The evidence of sexual 

 reproduction in Ectrogella is thus very meager and 

 inconclusive, and until further proof is found the 

 presence of sexuality in this genus must be regarded 

 as highly questionable. 



E. BACILLARIACEARUM Zopf, 1884, I.e., pi. 16, figs. 

 1-21. 

 Cymbanche fockei Pfitzer (pro parte), 1869. Sitz'b. 



"Niederrh. Ges. Nat. Heilk. 26:2-21. 

 Olpidium gilli de Wildeman, 1896. Ann. Soc. Beige 

 Micro. 20:41; Gill, 1893. Jour. Hoy. Micro. Soc, 

 1893:1, pi. 1. 



Zoosporangia solitary or up to 30 in a cell, smooth, 

 hyaline, oval, elongate, cylindrical, vermiform, 4-9 fi 

 in diameter and up to 200 jx in length with 1 to 1 1 

 short exit tubes or papillae in single or opposite 

 rows, which project between the separated valves 

 of the diatom cell on the girdle side and stain in- 

 tensely violet with chloro-iodide of zinc. Zoospores 

 diplanetic ; primary zoospores pyriform, 2Xlft 



with a refractive spot at the anterior and numerous 

 granules at the posterior end and two rudimentary 

 (?) equally long, 4 /x, flagella inserted laterally in 

 a slight indentation near the anterior end ; emerging 

 fully formed and swimming directly away, later 

 coming to rest and encysting; secondary zoospores, 

 oval 2 X 4 /"■ ( ?) with a tapering anterior end, near 

 which arise two unequal flagella, and one to several 

 refractive granules near the posterior end. Resting 

 spores unknown. 



Parasitic in Synedra lunalaris, Synedra sp. ; 

 Gomphonema sp. and Pinnularia sp. in Germany 

 (Zopf, I.e.); Synedra sp. and Gomphonema sp. in 

 Belgium (de Wildeman, '90, '93, '94, '95); Pleuro- 

 sigma attenuatum, Synedra sp., Pinnularia sp., Coc- 

 conema lanceolatum and Nitzschia sigmoidea in 

 England (Gill, '93; Smith and Ramsbottom, '17); 

 Synedra ulna, Pinnularia sp., Gomphonema sp., and 

 Meridion circulare, in Hungary (Scherffel, '25; 

 Domjan, '35), and Pinnularia sp. in New York, 

 U. S. A. (Sparrow, '33). This species was found in 

 great abundance in Nitzschia sigmoidea by the au- 

 thor during the summer of 1942 at Beaufort, North 

 Carolina. 



This is the type species of the genus, and although 

 it apparently occurs abundantly in nature it is still 

 incompletely known. Petersen regarded it as a prob- 

 able species of Pleotrachelus with numerous exit 

 tubes arranged in rows. 



The question of whether or not the organism 

 which Gill described relates in entirety to this spe- 

 cies has been the subject of much discussion. As is 

 indicated in the synonomy above de Wildeman be- 

 lieved that the sporangia shown in figures 1-8 by 

 Gill relate to a species of Olpidium since only a sin- 

 gle elongate exit tube is present, while the thalli 

 shown in figure 9 relate to E. bacillariacearum. Min- 

 den recognized O. gilli as a valid species, but Scher- 

 ffel was undecided about its validity. He maintained, 

 however, that it as well as Van Heurck's fungus is 

 not identical to Zopf 's or to any of his own species of 

 Ectrogella, and believed that figure 9 of Gill may 

 relate to E. bacillariacearum or Aphanomycopsis. 

 Scherffel failed to observe Zopf's species in Pinnu- 

 laria and Gomphonema, and he was accordingly of 

 the opinion that Zopf's figure 23, plate 16, may re- 

 late to Lagenidium brachystomum. 



Van Heurck ('99, p. 64, fig. 22) figured and de- 

 scribed an endophytic parasite with a single elon- 

 gate exit tube in Pleurosigma angulatum which is 

 strikingly similar to Gill's organism. Van Heurck 

 believed that his fungus may be identical to Gill's 

 species. 



As Fischer ('92) pointed out. Pfitzer's Cym- 

 banche fockei may perhaps relate in part to E. 

 bacillariacearum. Zopf ('84, '85), however, regarded 

 it a member of the Saprolegniaceae. It is also possi- 

 ble that the thick-walled structure with an eccentric 

 vacuole which Pfitzer described may be the resting 

 spore of this species. Pfitzer described this spore as 

 containing small starch grains like those found by 

 Pringsheim in Saprolegnia, but these bodies are ob- 



