60 THE LOWER FUNGI—PIIYCOMYCETES 



The host is infected by the uninucleate zoospore. This becomes 

 multinucleate and divides, so that the host cell often contains 

 several multinucleate myxamoebae. These grow and may come 

 in contact but are never completely fused. Each myxamoeba 

 forms its spores independently, and they may be in various 

 stages of completion in the same host cell. Prior to spore 

 formation the protoplasm of each myxamoeba segments into 

 uninucleate spore mother cells. Two divisions, believed to con- 

 stitute reduction, then occur, and the spore mother cell is cut 

 by two perpendicular planes into four uninucleate cells, each of 

 which assumes a cell wall and becomes a spore. These four 

 spores tend to remain permanently united. 



MolUard (1909) described a second species, T. triglochinis 

 Molliard, on a parasite occurring on Triglochin palustre. Galls 

 are formed on various parts of the plant above ground. The 

 life history of this organism is imperfectly known. A multi- 

 nucleate myxamoeba segments in the host cell into uninucleate por- 

 tions and these after several nuclear divisions again segment. 

 Tetrads of globose bodies, described by Molliard as spores, are thus 

 formed. Maire and Tison (1911) state that these lack a definite 

 cell wall and consequently are not comparable to the spores of 

 other members of the group. These authors have seen fit, 

 therefore, to erect a new genus Molliardia Maire & Tison for 

 this species, which they retain in the Plasmodiophoraceae only 

 provisionally. Until the species is better known it seems more 

 logical to retain it in Tetramyxa as a doubtful form. 



8. Sorosphaera Schroter (1886: 135). 



As founded by Schroter the genus Sorosphaera included only 

 one species, 8. veronicae Schrot., occurring in Europe on various 

 species of Veronica. It causes the formation of galls on various 

 parts of the plant, leaves, petioles, stems, etc. After infection 

 by the uninucleate, amoeboid zoospore the host cell becomes 

 greatly enlarged. The parasite grows, becomes multinucleate, 

 and divides, several multinucleate protoplasts thus coming to exist 

 in the same host cell. By host cell division " Krankheitsherde" 

 are formed as described for Plas7nodiophora, but direct migration 

 through the cell walls has not been observed. The several 

 multinucleate protoplasts in a single host cell increase in size, 

 but never fuse with one another. Although the nuclei of each 

 myxamoeba divide simultaneously, the nuclei of adjacent 



