CHAPTER XXIV 



The Culture Mount 



IN ORDER to identify species of fungi, it is often necessary to study 

 the character of their spores and their arrangement. These are char- 

 acteristically formed in the aerial portions of the colony. It is imprac- 

 ticable to study the colony directly under the microscope because of the 

 density of the growth and because the margin of the colony, where it might 

 be viewed, is entirely vegetative. If portions of a colony are removed and 

 mounted there results great disruption in the arrangement of the material. 

 However, characteristic spore forms may often be demonstrated in this 

 way. If mounts are made from a subculture on corn meal agar where the 

 vegetative growth is reduced, the direct mount is more satisfactory. A 

 hanging-drop preparation, in which the fungus is grown in a drop of liquid 

 medium in an enclosed space, has the disadvantage of a limited air supply, 

 which modifies the growth so that the vegetative structures predominate. 

 With the two methods to be described, the first of which we owe to Hen- 

 rici, the nature of spore forms may be satisfactorily studied. The first 

 is additionally valuable since permanent stained mounts may be made. 



1. COVER SLIP METHOD 



Step 1. Moistened filter paper or a damp blotter is placed on the bottom 

 of a Petri dish and sterilized in an autoclave at a pressure of 15 lb. for 

 20 minutes. 



Step 2. Six cover slips are cleaned, flamed and placed on the moist blotter 

 or filter paper. 



Step 3. A special medium is required. We use one containing 2 per cent 

 dextrose, 0.5 per cent peptone and 2 per cent agar. The medium must be 

 filtered through paper in order that any foreign particles may be removed 

 before sterilization. It is then melted, cooled to between 40 and 50 C. and 

 inoculated with spores of the colony to be studied. It should be well shaken 

 in order that a uniform suspension may be obtained. 



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