MICROSCOPICAL EXAMINATION OF MOLDS 105 



EXERCISE 36. MICROSCOPICAL EXAMINATION OF 



MOLDS 



Apparatus. Clean cover-glasses; clean slides; hand 

 lens or compound microscope; platinum needle and loop; 

 dissecting needle; glycerin, 10%. 



Cultures. Plate culture of mold. 



Method. The gross structure of a mold colony upon 

 a plate may be examined with a hand lens or by placing 

 the inverted Petri dish culture on the stage of the compound 

 microscope and examining with objective No. 3 and ocular 

 No. 1. The structure may be examined in detail as follows: 



1. Select a young colony which shows colored fruiting 

 bodies, if such are produced by the organism to be studied. 

 (Growth from natural or artificial media may be treated 

 in the same general way.) 



2. Using a sterile platinum needle, transfer a small 

 portion of the mycelium and fruiting bodies to a drop of 

 glycerin on a plain glass slide. If the mold growth is 

 closely confined to the surface of the media (as with Peni- 

 cillium or Aspergillus) , it is often desirable to cut out a 

 small piece of the medium bearing the mold and lift to the 

 slide by means of a sterile platinum loop. 



3. Tease out very gently, using dissecting needles or 

 common pins. The mold structure is extremely delicate, 

 so this operation must be performed with the utmost care. 



4. Place a cover-glass over the preparation. 



5. Examine with the microscope, using objective No. 3 

 and ocular No. 1. When a portion of mycelium bearing 

 fruiting bodies is found, examine with objective No. 7. 

 Draw the young and the old fruiting organs. 



DESCRIPTION OF PLATE III 

 Aspergillus, Showing Septate Mycelium, Conidiophore with 



Conidia, also Formation of As:ogonium. 



Penicillium, Germination of Spore, Formation of Mycelium, 



Septate Conidiophores with Conidia, Ripe Ascospore, 



