CHYTRIDIALES 461 



Vegetative system extramatrical or endobiotic without secondary 

 rhizoidal axes, tubular and septate throughout; sporangia extra- 

 matrical, of one type Coenomyces, p. 479 



CLADOCHYTRIUM Nowakowski, pro parte 



Cohn, Beitr. Biol. Pflanzen, 2:92. 1876 (sensu recent. Sparrow, Aquatic 



Phycomycetes, p. 305. 1943) 



(Fig. 30 I, p. 474) 



Thallus predominantly endobiotic, polycentric, eucarpic, consisting 

 of an extensive much-branched rhizoidal system on which are formed 

 irregular swellings, septate turbinate cells, and the rudiments of the 

 sporangia and resting spores; sporangia inoperculate, intercalary or 

 terminal on short lateral branches, with a discharge tube, often pro- 

 liferating; zoospores posteriorly uniflagellate, with a single globule, 

 formed in the sporangium, discharged through a pore at the tip of the 

 discharge tube; resting spores apparently asexually formed, borne like 

 the sporangia on the thallus, with a thickened smooth or spiny wall, 

 upon germination forming zoospores which escape through a discharge 

 tube or function as prosporangia. 



Species of the genus are primarily inhabitants of decaying plant 

 tissues such as those of Acorus, grass stems, Elodea, and the like. They 

 have also been found in the gelatinous envelope of Chaetophora and in 

 plants of Spirogyra, Coleochaete, and so forth. 



The genus as originally defined by Nowakowski included both 

 inoperculate and operculate forms. The latter were rightly segregated 

 from Cladochytrium by Schroeter (1893: 81) and placed in a new genus, 

 Nowakowskiella. From Nowakowski's description, C. tenue can be 

 considered typical of his genus. In that species the sporangia are 

 endobiotic, thin-walled, and discharge their zoospores through a tube 

 to the outside of the substratum. Resting spores in Cladochytrium are 

 borne on the thallus in the same fashion as are the sporangia (Sparrow, 

 1933c: 524, pi. 49, fig. 3; Karling, 1935: 449, figs. 21-29). At germination 

 they either form a discharge tube through which zoospores emerge or 

 function as prosporangia 



For a discussion of Cladochytrium versus Physoderma and Uro- 

 phlyctis, see Sparrow (1943: 306) and Karling (1950). 



