THE SIMPLE HOLOCARPIC BIFLAGELLATE PHYCOMYCETES 



so incomplete at present that this suggested rela- 

 tionship is largely hypothetical. 



WORONINA 



Cornu, 1872. Ann. Sci. Nat. 5 ser. 15: 176. 



(PLATES 1 AND 2) 



Thallus intramatrical, plasmodial, naked but im- 

 miscible with the host protoplasm; cleaving into 

 segments which become zoosporangia or resting 

 spores. Zoosporangia and resting spores united in 

 compact sporangiosori and cystosori respectively, 

 or lying loose and free of each other. Zoosporangia 

 usually spherical, oval or ellipsoid with a short exit 

 papilla or an elongate cylindrical and basally in- 

 flated exit tube. Zoospore pyriform or somewhat 

 kidney-shaped with one to several refractive gran- 

 ules, heterocont (?): emerging singly and fully 

 formed; occasionally liberated within the host cell; 

 swimming directly away in a comparatively slow 

 and even manner. Resting spores spherical, oval, 

 irregular and polygonal, with a smooth, spiny or 

 sculptured outer wall; producing one or several zoo- 

 spores directly in germination. 



This genus has been fully discussed by the writer 

 ('42) in relation to the phylogeny and relationships 

 of the Plasmodiophorales. It includes at present five 

 species most of which are incompletely known and 

 very doubtful, and in light of present-day knowledge 

 Woronina appears to be scarcely more than a dump- 

 ing ground for species with a plasmodial stage which 

 cannot be incorporated with certainty at present in 

 the Plasmodiophorales or Proteomyxa. The type 

 species, W. polycystis, has a life cycle almost iden- 

 tical to that of Octomyxa of the Plasmodiophoraeeae, 

 while W. glomerata resembles species of the zoo- 

 sporic Myxozoidia or Proteomyxa by its animal type 

 of nutrition. As a consequence these two species 

 have been included in the Plasmodiophorales (Spar- 

 row, '42) and the Proteomyxa (Zopf, '94; Seherffel, 

 '25) respectively. The other species, W. aggregata, 

 W. elegans, and W. asterina, are so imperfectly 

 known that it is impossible to determine their tax- 

 onomic and generic distinctions. Woronina must ac- 

 cordingly be interpreted for the time being as a in- 

 coherent and questionable group of species. It is 

 nonetheless phylogenetically significant, because it 

 includes organisms which appear to be transitional 

 forms between the Proteomyxa, Plasmodiophorales, 

 and simple, holocarpic biflagellate oomycete-like 

 fungi. Numerous undiscovered Woronina-like spe- 

 cies doubtless exist, the discovery of which may pos- 

 sibly bridge the present-day gaps. 



Sparrow ('42) disposed of Woronina directly by 

 including it in the Plasmodiophorales without pre- 

 senting additional evidence of its relationship to 

 this order, but this disposition merely overlooks and 

 does not clear up the problems involved. Woronina 

 polycysiis will probably prove to be a plasmodio- 



phoraceous species closely related to Octomyxa 

 Achlyae, and in that event some of the remaining 

 species must be segregated in another genus. Woro- 

 nina glomerata may well be a member of the Proteo- 

 myxa as Zopf and Seherffel contended, but further 

 study is necessary to settle this point. 



Inasmuch as these two species differ in certain re- 

 spects their development will be described sepa- 

 rately. In W. polycysiis the contents of the zoospore 

 enters the host hypha as a naked protoplasmic mass 

 (PL 1, figs. 6-10), undergoes amoeboid changes in 

 shape, develops into a plasmodium-like thallus as it 

 feeds on the host protoplasm, and causes local hyper- 

 trophy (figs. 11, 12). 



At maturity the thallus cleaves into segments 

 (figs. 13, 14) which develop into zoosporangia (figs. 

 15, 16) and form a typical sporangiosorus. As in 

 Octomyxa, the peripheral zoosporangia are usually 

 independent with a single exit papillae, while the 

 deeper lying ones may be confluent with a common 

 papilla for zoospore emission. Each sporangium pro- 

 duces a number of biflagellate zoospores (figs. 18, 

 19) which reinfect the host hyphae. As the culture 

 becomes older, the mature thalli cleave into small 

 segments which become the resting spores. These 

 remain closely attached and form compact cystosori 

 of various sizes and shapes (figs. 23—25). As in 

 Ligniera and Polymyxa, the cystosori may be elon- 

 gate, irregular, flattened, oval and almost spherical, 

 and include a few to numerous polygonal spores, 

 each of which produces one zoospore in germination. 



As to the structure of the zoospores there is, how- 

 ever, considerable disagreement among students of 

 this species. Fischer described and figured them as 

 ellipsoid (fig. 1) with a slight indentation at one 

 side and two slightly unequal flagella. The shorter 

 flagellum arises from the anterior end and extends 

 forward in swimming, while the longer one is in- 

 serted laterally and projects backward. It must be 

 noted, however, that Fischer's description was not 

 applied directly to W. polycystis but related to the 

 zoospores of Rozella, Olpidiopsis, and IVoronina as 

 a group. Cook and Nicholson ('33), on the other 

 hand, described the zoospore as spherical (fig. 3, 4) 

 with two anterior flagella which lash back and forth 

 in breast-stroke fashion in swimming. These work- 

 ers were non-committal about the relative lengths of 

 the flagella, but most of the figures show them to be 

 equal in length. One of their figures (fig. 3), how- 

 ever, shows flagella of unequal length. If the zoo- 

 spores are anteriorly biflagellate, as Nicholson and 

 Cook contended, and heterocont as Fischer reported, 

 they do not differ fundamentally from those of the 

 Plasmodiophorales. In view of the wide differences 

 in observation it is not altogether improbable that 

 what is now called W. polycystis may relate to more 

 than one organism or species. Further critical stud- 

 ies of this species are therefore highly essential. 



So far schizogony has not been reported in W. 

 polycystis, and nothing is known about the type of 

 nuclear divisions in the vegetative thallus. This 

 parasite has never been studied critically from fixed 



