I.AHENIDIACEAE 



71 



tions have yet been made to determine whether the 

 ■oospores carry the potentialities of one or both 

 sexes. In some of the unicellular species separate 

 thalli may function as male and female gametangia, 

 but it has not been proven that they represent dis- 

 tinct male and female strains. In light of our meager 

 present-day knowledge it would be premature to 

 discuss homo- and hcterothallisin in the Lagenidia- 

 ceae. 



In some species the unicellular th alius may divide 



at maturity into two cells which then function as 

 niab- and female gametangia, respectively. In most 



species, however, the female gametangium is usu- 

 ally larger, more vesicular, and frequently barrel- 

 shaped, while the so-called antheridium is usually 

 elongate and tubular. In Lagena, as noted before, 

 the unicellular thalli which fuse are equal in size and 

 indistinguishable. For this reason, the terms oogonia 

 and antheridia may be used only tentatively and 

 with reservation for the sexual organs in the Lageni- 

 diaceae. Differentiation of an egg cell and periplasm 

 in the female gametangium has not been convinc- 

 inglv demonstrated, but the ooplasm may contract 

 and aggregate toward the conjugation tube or pore 

 during plasmogamy. Shortly before fusion a con- 

 necting pore is formed between the two gametangia. 

 or the antheridium forms a tube or canal which pro- 

 jects into the oogonium. In Lagena, however, the 

 tube fuses with the surface of the oogonium without 

 entering it. The content of the antheridium then 

 slowly flows into the oogonium and fuses with the 

 ooplasm, after which the zygote becomes invested 

 with a thick wall. The resting spore thus formed lies 

 free in the oogonium, resembles the oospore of the 

 higher OomyceteS, and is generally referred to in tin- 

 literature as an oospore. In some species the antheri- 

 dium is lacking, with the result that the resting 

 spores are formed parthcnogeneticallv. 



The cytology of sexual reproduction from fixed 

 and stained material has been studied in only one 

 species, and very little is known about the gametic 

 nuclei and their behavior during plasmogamy and 

 karvogamy in the family as a whole. Until more is 

 known about these developmental phases the rela- 

 tionships of the I.agenidiaceae with the Saproleg- 

 niales and Peronosporalcs will remain obscure. 



As it is herewith presented the I.agenidiaceae in- 

 cludes Lagenidium, Myzocytium, and Lagena. The 

 first two genera are very similar and appear to be 

 closely related, and in light of present-day knowl- 

 edge it is questionable whether they should be sepa- 

 rated. As Cook '88 i has already noted, the differ- 

 ences are perhaps only specific instead of generic. 

 Lagenidiopsis is merged with Lagenidium, while 

 Achlyogeton and Mitochvtridium are excluded be- 

 cause of their uniflagellate zoospores. Restieularia 

 is listed as doubtful genus, but it may possibly prove 

 to be identical to and synonymous with Lagenidium. 

 Its reported isogamous and zygomveetous type of 

 sexual reproduction is very similar to that of /,. sac- 

 culoidet. On the other hand, future studies and dis- 

 coveries may necessitate the inclusion of Lagena. 



Restieularia and /.. sacculoides in a separate family 



because of their characteristic method of sexual re- 

 production. Protascus is excluded from the Lageni 

 diaceae because of its lack of zoospores. A full de 

 SCription and illustration of this genus is neverthe- 

 less presented here to emphasize again to mycolo 



gists the priority of Dangcard's Protascus over the 

 same generic name proposed by Wolk (13) for an- 

 other fungus. 



Gaumann and (iaumann and Dodge included 

 Ectrogella in the I.agenidiaceae, but subsequent 

 workers have not followed this viewpoint. The pies 

 enec, however, of isocont primary zoospores with 

 flagella inserted just below the anterior end anil 

 laterally biflagellate heterocont secondary swarm 

 spores indicates a closer relationship, as Scherffel 

 has pointed out, with the Saprolegniaceae. Tokunaga 

 included Aphanomycopsis in this family on the 

 grounds that it lacks a typically developed mycelium 

 and is holocarpic. The shape, structure, size and 

 general appearance of the th alius and zoospores are 

 strikingly like those of the Lagenidiaceae, and in the 

 encystment of the swarmspores in a cluster at the 

 mouth of the exit tube this genus is similar to L. 

 Oedogonii. Furthermore, the locally paunchy cell in 

 which the asexual or possibly parthenogenetic rest- 

 ing spore is formed is quite like the oogonium in 

 species of Lagenidium. There is thus good structural 

 evidence to support Tokunaga's viewpoint. Whether 

 certain stages of Borzi's Rhizomyxa belong here is 

 also problematical. Its reported mode of sexual re- 

 production is nonetheless strikingly similar to that 

 of Lagenidium and Myzocytium, with the exception 

 that an egg cell and periplasm are formed before 

 fertilization occurs. In the latter character it is 

 somewhat similar to Pythiella. 



LAGENIDIUM 



Schenk, 1859. Verh. Phys. Med. Ges. Wursburg 



9 : 27. 

 Lagenidiopsis de Wildeman, 1896. Ann. Soc. 



Belg. Micro. 20: 109. 



(plates 19, 20) 



Thalli intramatrical, solitary or numerous, con- 

 fined to one cell or extending through several host 

 cells; frequently elongate, straight, crooked, curved, 

 irregular, coiled, tubular, hypha- and mycelium 

 like, with numerous blunt protuberances; lobed. 

 branched or unbranched. slightly constricted or un- 

 COnstricted at the cross walls; multicellular or uni- 

 cellular, the latter continuous, globular, oval, ellip- 

 soidal, sac-like and irregular; often attached to tin- 

 host cell wall by the infection tube and zoospore 

 case; holocarpic. transformed into sporangia or 

 gametangia at maturity. Sporangia of the same 

 shape and size as the individual segments and uni- 

 cellular thalli, with one to several exit tubes of vary- 



