APPEARANCE OF GROWTH ON CULTURE MEDIA 223 



and the internal structure as determined by a low-power 

 lens are often of almost diagnostic value. Also in the case 

 of the gelatin plates, the character of the liquefaction is 

 important. Figs. 156 to 164 show some of the commoner 

 characteristics to be noted. 



Fig. 165. — A small mold colony, 

 natural size, as viewed by trans- 

 mitted light. 



Fig. 167.— a portion of the thin 

 edge of the same colony as seen with 

 the low-power objective. X 100. 



Fig. 166. — The same colony 

 viewed by reflected light. 



Fig. 168. — A single fruiting body 

 (sporangium) from the same colony 

 as seen under the low-power ob- 

 jective. X 100. 



Colonies of mold frequently appear on plates. These are 

 readily differentiated from bacterial colonies after a little 

 experience. With the naked eye usually the fine radiations 

 of the edge of the colony are apparent. The surface appears 

 duller and by reflected light more or less "fuzzy." With 

 the low-power objective the relatively large, branching 

 threads of the mold (mycelia) show distinctly. Also the 

 large fruiting bodies (sporangia) are easily distinguished 

 Figs. 165 to 168 illustrate a common black mold (Rhizopiis 

 nigricans) . 



