FUNGUS OCCURRING IN PULVINARIA INNUMERABILIS. 



them only the agglutination test. With these the reaction was 

 not so pronounced as with the yeast-like forms in culture, but 

 nevertheless distinctly positive. Unfortunately by the time the 

 animals had been immunized (early May) the number of yeast- 

 like cells in the insects had decreased and the reaction could not 

 be so readily observed as in the cultures, or so well as it might 

 have been several weeks earlier in the spring when the insects 

 contained innumerable, separated, oval cells. The data from the 

 rabbit experiments has, however, convinced us that there can be 

 practically no question that the organism cultivated is actually 

 the one present in the insects. Furthermore, since we have never 

 failed to observe it in living scales from this locality, and since 

 Putnam (v. antca, p. 301) found it invariably present in Iowa, it 

 is undoubtedly present regularly in Pnlvinaria inmimerabilis. 



CULTURAL CHARACTERISTICS OF THE FUNGUS. 



As stated at the outset, we wished to grow the symbiont on arti- 

 ficial media, not only to describe it adequately, but to determine 

 as completely as possible its physiological activities. In order to 

 do this, sub-cultures from the original isolations were planted 

 upon various media, such as are in general use by bacteriologists 

 and mycologists. From these, the following observations were 

 made. 



Growth on Solid Media. 



Potato Gelatine Colonies. Growth rapid ; after 72 hours, cot- 

 tony with flocculent elevated center and filamentous edge, diam- 

 eter of center I mm., width of margin I mm. Liquefaction cup- 

 shaped. 



Nutrient Gelatine Colonies. Growth slow ; after 72 hours, 

 rounded, with central elevation. Diameter 0.3 mm., with roundly 

 lacerated edge. Liquefaction cup-shaped. 



Potato Agar Colonies. Growth rapid; after 72 hours, fila- 

 mentous, ciliate (sub-surface) or rounded (surface). Disk when 

 present, smooth ; elevation convex ; edge of round colonies smooth, 

 that of irregular colonies radiately filamentous or ciliate. Internal 

 structure finely granular. Diameter 1.5-2.5 mm. 



Nutrient Agar Colonies. Growth slow ; after 72 hours, round, 



