50 THE LOWER FUNGI— PHYCOMYCETES 



form a hollow sphere). In a later and more extensive paper 

 they (Maire and Tison, 1911) erect two new genera, Molliardia 

 and Ligniera, and present a somewhat revised classification in 

 which they stress as of primary significance the question of 

 w^hether a given organism results in hypertrophy of the host. 



Although the genus Spongospora Brunchorst (1887), now 

 regarded as a member of the group, was described relatively 

 early, its existence was overlooked or ignored by all of these 

 later writers. It was demonstrated to be an undoubted member 

 of the group by Osborn (1911 a) at about the time that Maire 

 and Tison published their second paper. Subsequently, several 

 additional genera have been described by other authors. These 

 are all discussed below and in spite of fragmentary data in the 

 case of some species, the attempt is made to present a complete 

 picture of the family as it exists today. 



The writer is not the first to incorporate the Plasmodi- 

 ophoraceae in the fungi. Gaumann (1926) and Gaumann and 

 Dodge (1928) incorporate the group in the Archimycetes, and 

 emphasis has been placed by various investigators on facts which 

 seemed to them to justify the inclusion of the group in the fungi. 

 There has been considerable diversity of opinion expressed in re- 

 cent years, however, as to the relationships of the group. Pavil- 

 lard (1910) concludes that these forms are a branch of the 

 Myxomycetes in which modifications have resulted from the 

 parasitic habit. Schwartz (1914), while admitting that they are 

 related to the Myxomycetes, regards the differences as so great 

 that he treats them as intermediate between this group and the 

 Chytridiales. Maire and Tison (1911) feel that they have origi- 

 nated from the Chytridiales, while Cook (1926) thinks that they 

 show relationship with the Protozoa. 



Students of the cytology of these forms have been impressed 

 by the great similarity which the various genera and species 

 show in the aspects of their nuclear behavior, and by the fact 

 that they differ from other groups in exhibiting in their life cycle 

 two entirely different types of nuclear division. One type occurs 

 throughout the growth of the thallus or myxamoeba; the other 

 immediately precedes spore formation or zoospore delimitation, 

 and consists of two successive divisions which are believed to 

 constitute reduction. The nuclear division which occurs during 

 the growth period and which may be termed somatic has been 

 commonly termed the "cruciform division" or protomitosis. 



