WIXGE, CYTOLOG. STUDIES IN THE rLASMODIOPHORACE.E. 31 



The designations employed by the various authors for 

 the organs of the Plasmodiophoraceae and their relations are 

 often varying. Especially disagreeing are the opinions as to 

 whether it is allowable to say, that a »spore» at the germina- 

 tion may be converted into a »sporangium» since the contents 

 of the »spore» forms several zoospores. It is likewise evident 

 how difficult it is to keep apart the definitions »spore-mother 

 cell» and »sporangium». The aggregations of spore-mother 

 cells in one form are plainly perfectly homologous with the 

 sorosporangia in another. — As regards this matter it must 

 be remarked, that as the definition »spore» is very elastic, 

 we can scarcely be wrong in using the denotation »spores» 

 in the Plasmodiophoraceae even though these at the germi- 

 nation prove themselves capable of further divisions, thus 

 reminding us of yet indifferentiated sporangia. When we 

 compare the conditions in the Plasmodiophoraceae with Sor- 

 olpidium and Pyrrhosorus it becomes moreover quite evident 

 that the myxamoebae in the former, form spore-mother cells, 

 where in the latter they form »sorosporangia» — (since the 

 spore-mother cells are here formed within a wall). The cir- 

 cumstance that the spore-mother cells within the w^all of the 

 »sporangium» are outdifferentiated seems to favour the 

 belief that a reductive division takes place at the spore- 

 formation like in the Plasmophoraceae and all the higher 

 plants where spore-mother cells are formed in the sporangia 

 (micro- and macro-sporangia). It is thus the entire amoeba 

 which after having become walled may be termed sporan- 

 gium — not the spore-mother cells as Nemec has it. A re- 

 ductive division in Sorolpidiiim cannot be expected to be 

 found prior to the aggregational stage, but at the formation 

 of the zoospores. In case Nemec's strange theory should be 

 carried out that the spores of the true Plasmodiophoraceae 

 are unispored sporangia, the curious fact would arise that 

 sporangia are formed in these as a result of the reductive 

 division at the formation of tetrades. We can, therefore, not 

 agree with his declaration that his theories^ are »Möglich- 

 keiten , die psychologisch wohl zu erklären sind». 



The conditions in Sorolyidium and Pyrrhosorus may on 

 the whole be paralleled with the microsporangia of the phane- 

 rogams in which spore-mother cells are formed which again 

 form spores. If a reductive division also proves to appear 



