88 



THE SIMPLE HOLOCARPIC BIFLAGELLATE PHYCOMYCETES 



among the zoosporangia; oogonia spherical, 15— 

 25 p., oval, ellipsoidal and egg-shaped; antheridia 

 fusiform, and elongate, 8-12 ti X 16 X 18 ti, and 

 narrowly spindle-shaped. Oospores spherical, 8— 

 25 fx, ellipsoid, 14-22 /n, and somewhat angular, 

 hyaline with a smooth thick, two-layered wall and a 

 large eccentric refractive globule ; germination un- 

 known. 



Parasitic in Mougeotia sp., Mesocarpus sp., and 

 M. pleurocarpus, Spirogyra sp., Zygnema sp., Cos- 

 marium connatum, C. botrytis, Micrasterias rot at a, 

 and Closterium didymotocum in Germany (Schenk, 

 I.e.; Lindstedt, I.e.; Reinsch, '78; Zopf, '84; Schroe- 

 ter, '86; Minden, 11); various algae in France 

 (Cornu, '69); Cladophora sp. and Arthrodesmus 

 sp. in Russia (Sorokin, '83, '89) ; Spirogyra sp., 

 Zygnema sp., and Cosmarium sp. in Belgium (de 

 Wildeman, '93, '95, '96) ; Cladophora sp. and Spiro- 

 gyra sp. in Roumania (Constantineau, 01); Mou- 

 geotia sp. and a dead insect in Denmark (Petersen, 

 '09, '10; Lind, '13) ; Spirogyra sp. in China (Skvort- 

 zow, '27), Cladophora sp., C. kuetzingiana, Zygne- 

 ma cruciatum, Mougeotia sp., Closterium acerosum 

 and Spirogyra sp. in Iowa, Montana, and New York, 

 U. S. A. (Martin, '27; Graff, '28 ; Sparrow, '32, '33; 

 Thompson, '31) ; Spirogyra sp. in Bulgaria ( Valka- 

 nov. '31) ; S. affinis in India (Chaudhuri, '31 ; Mund- 

 kur, '38); Spirogyra jurgensii, Spirogyra sp., and 

 Cladophora sp. in Japan (Tokunaga, '31) ; Spiro- 

 gyra sp. and Mougeotia sp. in Hungary (Scherffel. 

 '02; Domjan, '35); Spirogyra sp., Mougeotia sp., 

 Zygnema sp., Mesocarpus sp., Closterium leibleinii, 

 and Closterium sp. in Bohemia (Cejp, '32, '35). 



This is the most widely distributed species of 

 Mysocytium, but although it has been observed and 

 described a great number of times, there are still 

 numerous differences of opinion in the literature 

 about certain of its developmental phases. Cornu, 

 Walz, Zopf. Sparrow ('32) and Thompson claimed 

 that the sporeplasm emerges through the exit tube 

 and then undergoes cleavage into zoospores within 

 a vesicle as in Pythium, while other investigators 

 have maintained that the swarmspores are delimited 

 to some degree in the sporangium, emerge singly in 

 succession, and then complete their development in 

 the extramatrical vesicle. Sparrow described the 

 zoospores as only 3.6 X 5.4 /u. in size, but Constan- 

 tineau claimed that they vary from 5 X 6 to 

 6 X 9 /"■• This difference may be due to unequal and 

 abnormal cleavage, whereby large zoospores are 

 formed, as has been described by Thompson. The 

 writer has often found abnormally large zoospores 

 with four to twelve flagella. 



Dwarf thalli consisting of one or two segments 

 often occur in this species, and for this reason the 

 author is inclined to agree with Fischer ('32), de 

 Wildeman ('96), and Minden that Sorokin's Bicri- 

 cium transversum and B. naso may possibly relate 

 to this species. Petersen, however, was doubtful 

 about the latter species' identity. It is to be noted 

 here that the exit tubes of B. naso are inflated and 

 globular at the base and extend far beyond the sur- 



face of the host cell. If this character proves to be of 

 specific diagnostic value B. naso, on the other hand, 

 may possibly represent dwarf thalli of M. megas- 

 tomum. Sorokin's Olpidium tuba and 0. saccatum 

 may also possibly be reduced specimens of M. pro- 

 liferum. Cornu ('77) was of the opinion that the 

 parasites which Reinsch (pi. 17, figs. 6-12) found 

 in various desmids relate to this species also, but 

 Zopf ('84) believed that the one with partheno- 

 genetic oospores figured in Closterium didymotocum 

 is not identical but only closely related to M. pro- 

 lifer um. 



Myzocytium irregulare Petersen (09, '10) which 

 parasitizes Micrasterias and Cosmarium may pos- 

 sibly be nothing more than dwarf and irregular thalli 

 of M. proliferum. This species is characterized 

 primarily by irregular and lobed sporangia, the short 

 exit tubes of which are greatly inflated inside of the 

 host wall (fig. 49). Nothing is known about the 

 structure and shape of the zoospores, gametangia 

 and oospores. Petersen believed that all forms which 

 had been previously described in flat and small 

 desmids, exclusive of those in Closterium, relate to 

 M. irregulare, and that of M. proliferum should in- 

 clude only the regular elongate and chain-like forms 

 which occur in the filamentous algae and elongate 

 desmids. He was further of the opinion that M. 

 irregulare may also possibly relate to Lagenidiutn 

 or represent a new genus. Chaudhuri supported the 

 latter viewpoint, but Cejp ('33, '35), who found M. 

 irregulare in Micrasterias rotata, M. truncata, Cos- 

 marium sp., and Pleurotaenium sp. in Bohemia, 

 thought it may relate to Mysocytium. So far sexual 

 reproduction and oospores have not been observed. 

 Until more is known about the life history of this 

 parasite and extensive inoculation experiments have 

 been made, the validity of Petersen's species remains 

 doubtful. 



Myzocytium lineare Cornu ('72, p. 21) is imper- 

 fectly known and very doubtful, and Minden was of 

 the opinion that it relates to a species of Lageni- 

 diutn. Cornu described it very briefly as simple and 

 sparingly branched witli elongate, linear sporangia ; 

 but he did not figure it. He ('77) also believed that 

 the thalli shown in Reinsch's (I.e.) figures 5 and 14, 

 plate 17, relate to M. lineare. The data relative to 

 Cornu's fungus are too fragmentary to warrant any 

 definite conclusions, so that the validity, identity, 

 and synonomy of this form are largely a matter of 

 personal interpretation. 



M. VERMICOLUM (Zopf) Fischer, 1893. Rabenh. 



Kryptog'fl. 1. 4:73. 

 M. proliferum var. vermicolum Zopf, 1884. Nova Acta 



Ksl. Leop.-Carol. Deut. Akad. Nat. 47: 167. PI. 14, 



figs. 35-37. 

 Bicriciuin lethale Sorokin, 1883. Arch. Bot. Nord France 



2: 37. Fig. 45. 1889. Rev. Mycol. 11: 138. PI. 78, figs. 



72-74. 



Zoosporangia spherical, oval, ellipsoidal, irregu- 

 lar, lobed; occurring singly and isolated, in pairs, or 

 up to 12 in a linear chain, with 1—2 wide exit tubes 

 of variable length. Zoospores oval, heterocont (?). 



