64 THE LOWER FUNGI— PHYCOMYCETES 



small polygonal cells, the spores. Between the two layers a 

 small lumen occasionally occurs. This indicates that the plates 

 are in reality much flattened hollow spheres or ellipsoids, and 

 the genus is believed by Winge to be very close to Sorosphaera. 

 Winge did not observe infection nor the uninucleate stage of the 

 myxamoeba. Later stages were studied, and the form seems 

 to correspond in the main to other members of the group. Young 

 myxamoebae and mature spore balls were observed together 

 in the same host cell. The individual spores are finally spherical. 

 Spore germination was not observed. 



5. Spongospora Brunchorst (1887). 



The spore balls of Spongospora are, as the name signifies, 

 tiny sponge-like aggregations of spores. The interior of the 

 ball, unlike that of Sorosphaera, is essentially solid, and is tra- 

 versed by broad fissures which open to the surface as prominent 

 lacunae (Fig. 6). In shape the ball is globose or 

 somewhat elongated, and the individual spores, 

 while actually polyhedral from mutual pressure, 

 are potentially spherical. 



The genus contains the single species, Spon- 

 gospora subterranea (Wallroth) Lagerheim, cause 

 of powdery scab of potatoes. When Brunchorst 

 Fig. 6. — Spongo- erected the genus he named the organism S. 

 (Waiir^othT LTger- i'olani, not realizing that the earlier name Ery- 

 heim. A single spore sibe subterrauea Wallroth (1842) had been given 

 ball. {Original.) ^^ .^_ rj.^^ identity of the two forms was 



recognized by Lagerheim (1892: 104), and the existence of other 

 early synonyms was noted. Martins (1842: 28) named the 

 species Protomyces tuberum solani, and Berkeley (1846: 33) 

 called it Tubercinia scabies. The organism came into prominence 

 through the papers of Massee (1908) and Johnson (1907; 1908; 

 1909) on economic aspects of the potato disease. Massee used 

 the name Spongospora scabies (Berkeley) Massee. Later the 

 organism was studied cytologically by Osborn (1911 a, 6) 

 and Home (1911); while Melhus (1914 h) and Kunkel (1915) 

 have published on its life history. 



When Brunchorst established the genus he saw a plasmodium- 

 like stage associated with the spore balls, and regarded the 

 organism as a relative of the slime moulds. Lagerheim opposed 

 this point of view, and Maire and Tison failed to include the genus 



