CHYTRIDIALES 437 



ascribed to Rhizidium, Diplophlyctis, Nowakowskiella, and Nephro- 

 chytrium and are figured in older described chytrids such as ? Rhizidium 

 lignicola Lindau and the aforementioned Amoebochytrium rhizidioides 

 Zopf. Several observers of undoubted Rhizophlyctis rosea have not, 

 however, reported them ; nor have they been seen in material of it by 

 this author save once. 



Since Karling (1947b: 65) has confirmed endooperculation in Rhizo- 

 phlyctis rosea and verified it for other rhizophlyctoid fungi as well as 

 for species of Nowakowskiella and "Nephrochytrium," there is little 

 doubt that the observations concerning this structure are correct. The 

 present author, who has attempted to assemble all available published 

 data as well as depend upon his own observations, concludes that 

 endooperculation as opposed to true operculation is an unstable 

 character. Under certain conditions one might then expect to find it 

 in any chytrid, but perhaps especially in those sporangia in which the 

 discharge papilla early in development liberates its gelatinous contents 

 unaccompanied by immediate zoospore discharge. Haskins and Weston 

 (1950) have expressed a similar opinion. Species of Rhizophlyctis are 

 evidently particularly prone to form endoopercula. Few species of 

 rhizophlyctoid fungi, since Johanson's study, have been described as 

 without them. They have also been demonstrated in the true operculate 

 as well as the inoperculate types. 



Should subsequent observations on Rhizophlyctis species prove 

 endooperculation to be a constant character, comparable with oper- 

 culation in Chytridium and Nowakowskiella, recognition of Karlingia 

 and generic segregation of such forms as Diplophlyctis amazonense 

 and Nowakowskiella gramdata would seem justified. In this publication 

 the type of Karlingia is considered a true Rhizophlyctis. Hence, the 

 species of Karlingia with exoopercula formed from wall material are 

 better accommodated in a new genus, Karlingiomyces (see p. 559). 



In Rhizophlyctis, as elsewhere, variations in thallus development 

 occur. Not only does the sporangium occasionally form at the tip of a 

 germ tube from the encysted spore body, but Karling (1947b) has noted 

 the production, though rare, of polycentric thalli of limited extent. 



