MORPHOLOGY IN CULTURE 



309 



or other capsule-demonstrating techniques are used. In most newly 

 isolated strains the capsular material is produced in sufficient amounts 

 to make the colony semi-fluid so that it tends to sag or flow slowly 

 toward the bottom of the slant when the latter is incubated in a 

 vertical position. The color is very light brownish tan. 



In older cultures, and particularly in some strains, the capsule 

 becomes very thick. It is usually eccentric so that it barely covers 



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 4 



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Fig. 124. C ryptococcits neoformans: left, young culture; right, old culture. 



or even exposes the cell wall on one side, and it extends as a thick, 

 striated, husk-like structure around the rest of the cell (Fig. 124). 

 The thin area in the capsule marks the point where budding has 

 recently occurred, where buds are still attached, or where budding 

 may continue to take place. The thick capsule may, in other in- 

 stances, enclose both parent cell and bud. In these old cultures there 

 are exceptions to the previous statement that the bud communicates 

 with the parent cell by a comparatively narrow opening. Occa- 

 sionally in old cultures the neck is as wide as any portion of the 

 bud and many bizarre forms are observed. 



An examination of the culture may not give sufficient basis for the 

 differentiation of C. neojormans from similar saprophytic species. In 

 such cases it is useful to inject 0.05 ml. of a suspension of the fungus 



