CHAPTER XXII 



Characteristics of Fungi on Culture 



SPECIES of fungi may usually be recognized by their cultural appear- 

 ance. With experience one may recognize many species, as one would 

 a human acquaintance, without having to see all the features. At other 

 times, particularly when variants appear, all the characteristics of the 

 micro-organism may be required in order to determine its nature. 



The information to be mentioned in this chapter will usually suffice 

 for diagnosis. It is well to examine the inoculated culture medium after 

 two or three days (to see if contaminating organisms are present), after 

 five to seven days (for the early characteristics) and finally after 10 days 

 to three weeks (for the characteristics of the full-grown prime colony). 



1. ROUTINE EXAMINATION 



1. The date of inoculation should be placed on the label of the culture 

 tube together with some means of identification. When the colony is exam- 

 ined, the age may then be readily determined. 



2. The kind of medium used should be noted. It may again be empha- 

 sized that even slight differences in the composition of the medium may 

 alter the cultural appearance. On growths sent to us for identification, we 

 often find it necessary to transfer the culture to our own standard medium 

 to develop the characteristics of the colony with which we are familiar. 



3. The number of days before growth is first noted is significant. 



4. Rapidity of growth is indicative. If a colony is at prime in seven to 

 10 days it may be considered a fast grower; if three weeks elapse before 

 it can be recognized, it is a slow grower; most fungi are of intermediate 

 character. The rate of growth is influenced by many factors, such as tem- 

 perature, the depth of the agar and the type of culture medium. In the 

 summer the rate of growth of fungi is noticeably faster than during the 

 winter months; the greater the deptli of agar the faster and more luxuriant 



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