24 



THE SIMPLE HOLOCARPIC BIFLAGELLATE PHYCOMYCETES 



P. littoralis, Stictyosiphon tortilis, Striaria atten- 

 uata, Akinetospora sp., Ectocarpus sp., E. confer- 

 voides, E. sandrianus, and Punctaria sp., in Den- 

 mark and Greenland (Petersen, '05 ; Sparrow, '34) ; 

 Stictyosiphon corbierei and Ectocarpus sp. in 

 France (Pierre Dangeard, '34), causing marked 

 hypertrophy and destruction of the infected cells. 

 Magnus ('05) claimed to have seen it in marine 

 algae at Kiel also as early as 1872. 



As is evident in the synonomy given above this 

 type species of the genus has undergone numer- 

 ous taxonomic changes. Wright, Hauck, Rattray, 

 Fischer ('92) and Schroeter ('97) placed it in the 

 genus Rhizophidium, but in '99 Wille transferred it 

 to Olpidium because of the lack of a rhizoidal sys- 

 tem. In 1905 Magnus called attention to the fact 

 that the sporangia burst through the host cell and 

 become partially extramatrical with one to several 

 broad exit tubes or papillae, characters which are 

 unlike those of Olpidium; and he accordingly created 

 the new genus Eurychasma for Wright's species. 

 Finally, in 1925, Scherffel transferred it to Ectro- 

 gella. 



This species had doubtless been seen before its 

 discovery by Wright and mistaken for a stage in the 

 life cycle of its host. Wright and Rattray were of 

 the opinion that the reproductive organs of certain 

 marine algae described by Harvey (1862) and Kiit- 

 zing (1855, 1861) relate to this species. Magnus, 

 however, claimed that the latter workers had studied 

 and figured Chytridium plumulae. 



E. SACCULUS Petersen, 1005, Overs. K'gl. Dansk. 

 Videns. Selsk. Forh. (5):477, figs. VIII, 5, 8, 9. 



, Zoosporangia solitary, largely extramatrical, hya- 

 line, smooth, irregular, elongate, 80—184 ji high, with 

 one to three broad exit tubes; intramatrical portion 

 lobed and irregular. Zoospores and resting spores 

 unknown. 



Parasitic in Rhodymenia palmata and Halosac- 

 cion ramentaccum in Greenland, causing marked 

 hypertrophy and destruction of the infected cell. 



According to Petersen, this species differs from 

 E. dichsonii by the lobed and irregular shape of the 

 zoosporangia, particularly the intramatrical por- 

 tion. Although he did not observe the zoospores, he 

 believed that they may behave in the same fashion 

 as those of the previous species. On the basis of 

 present-day knowledge concerning Eurychasma it 

 appears to be a very doubtful species, and further 

 study may prove it to be identical to E. dichsonii. 

 Scherffel, on the other hand, believed that it may be 

 a species of Ectrogella. 



Whether or not Gran's ('00) Olpidium Lauderiae 

 parasitic in Lauderia borcalis belongs in Eury- 

 chasma or Ectrogella is a matter of dispute. Peter- 

 sen (I.e., p. 469) regarded it as a questionable spe- 

 cies of the former genus and renamed it E. Laud- 

 eriae. Scherffel thought that it may prove to be a 

 member of Ectrogella, and named it Ectrogella 

 Lauderiae. 



EURYCHASMIDIUM 



Sparrow, 1936. Biol. Bull. 70: 241. 



(plate 7) 



Thalli intramatrical, solitary or numerous, unicel- 

 lular, spherical, ellipsoid, irregular and lobed. Zoo- 

 sporangia solitary or up to eight in a cell, variously- 

 shaped with one or numerous exit tubes which may 

 end flush with the surface of the host cell or extend 

 beyond it. Zoospores diplanetic, encysting in polyg- 

 onal cysts at the mouth of the exit tubes, emerging 

 later and leaving the empty cysts behind ; relative 

 lengths and position of flagella unknown. Resting 

 spores unknown. 



Sparrow created this genus for the parasite of 

 Ceramium which Magnus first discovered in 1872 

 and described as Chytridium (Olpidium) tumi- 

 faciens. As is shown in Plate 7 it is very similar to 



plate 6 



Eurychasma dichsonii 



(Figs. 1, 3-5, 8-11, 14-17 after Sparrow, '34; fig. 2 after 

 Dangeard, '34; figs. 6, 7, 12, 13 after Lowenthal, '05; 

 fig. 18 after Wright, '77.) 



Fig. 1. Fixed and stained biflagellate heterocont zoo- 

 spores. 



Fig. 2. Biflagellate heterocont zoospores with a taper- 

 ing anterior end near which the flagella are attached. 



Fig. 3. Early infection stage of Striaria cell. 



Fig. 4. Enlarged algal cell with zoospore case and in- 

 fection tube attached. 



Fig. 5. Enlarged algal cell with small parasite within. 



Fig. 6. Naked young uninucleate amoeba-like parasite 

 with several pseudopods lying in cytoplasm of a Pyiaielta 

 littoralis cell; host nucleus at left. 



Fig. 7. Naked tetranucleate parasite in which only two 

 nuclei are visible; lying in the vacuole of a gametangium 

 of Pylaiella. 



Figs. 8-9. Distended host cells with vacuolate parasites; 

 exit papillae beginning to form. 



Fig. 10. Partially extruded parasite which has ruptured 

 the enveloping host wall. 



Fig. 11. Zoosporangium with a peripheral layer of zoo- 

 spores. 



Fig. 12. Longitudinal section of parasite before cleav- 

 age showing the protoplasm as a thin layer lining the 

 sporangium. 



Fig. 13. Longitudinal section of sporangium after com- 

 pletion of cleavage. 



Fig. 14. A "net-sporangium" in which all but two of the 

 zoospores have evacuated their cysts. 



Fig. 15. Sporangium with two exit tubes and a periph- 

 eral layer of encysted zoospores. 



Fig. 16. Portion of a "net-sporangium" showing emer- 

 gence of zoospore from a cyst. 



Fig. 17. Sporangium showing direct discharge of zoo- 

 spores without previous encystment. 



Fig. 18. Sporangia in cells of Ectocarpus granulosus. 



Fig. 19. Empty thallus of Eurychasma sacculus show- 

 ing irregular sac-like character of intramatrical portion. 

 Petersen, '05. 



