PLASMODIOPHORALES 775 



WORONINA Cornu 



Ann. Sci. Nat. Bot., V, 15: 176. 1872 

 (Figs.58 A-E, K-M, p. 778; 59 E-H, p. 786) 



Thallus unwalled, endobiotic, holocarpic, in walled-off portions of 

 the host (the walls those of the host), forming the rudiment of the 

 sporangia, sorus, or cystosorus ; sporangia grouped, each forming a pore 

 through which the biflagellate heterocont zoospores emerge; cysts thick- 

 walled, angular or spherical, generally closely aggregated into cystosori, 

 each upon germination functioning as a zoosporangium. 



Parasites of other Phycomycetes and green algae. 



Members of the genus are very animal-like in some of their features. 

 If ZopPs observations on the behavior of the plasmodium in Woronina 

 glomerata are unquestionably confirmed and extended the species will 

 provide a remarkable connecting link with Proteomyxa-like, protozoa. 



The best-known species, Woronina polycystis, is a common parasite 

 in Saprolegnia and Achlya. The observations of Fischer (1882) indicated 

 that the linear sequence of thallus development found in heavily infected 

 hyphae was not due to successive fractionation of a single thallus but 

 to multiple infection. A single zoospore gave rise to a single thallus and 

 the transverse septa were formed by the host, not the parasite. Cook 

 and Nicholson (1933), on the other hand, declare that the multinucleate 

 "Plasmodium" may, at the time of septation by the host, be divided 

 and that the segments produced may develop into full-sized thalli. In 

 this manner a series of plasmodia may be formed. They also noted 

 that the thallus feeds mainly upon the globules of oil present in the 

 host cells. 



The most recent study of Woronina polycystis is one by Goldie-Smith 

 (1954). Her most pertinent findings are the occurrence of protomitotic 

 nuclear figures (Fig. 58 K, p. 778) and the existence of the heterocont 

 zoospores that are typical of the Plasmodiophorales. 



She states that the zoospores, after a period of amoeboid activity on 

 the outside wall of the host cell, encyst and produce a curved germ tube 

 which effects penetration (Fig. 58 M, p. 778). She does not say whether 

 the numerous young plasmodia in the hypertrophied parts of the host 

 are each derived from a single zoospore or by the fragmentation of a 

 single plasmodium. In view of the many encysted zoospores found 



