16 



ISOLATION AND CULTIVATION OF FUNGI 



Spores as inoculum. If the fungus to be isolated produces 

 spores in sufficient abundance, concentrated suspensions of spores 

 in water can be made and either of two general methods of iso- 

 lation can be employed: (1) the streak method, or (2) the dilu- 

 tion method. 



The streak method is the oldest and simplest procedure. A 

 needle, bearing a loopful of spores suspended in water, can be 



Fig. 5. Materials used in isolating single spores by streaking. A. Poured 

 agar plate over whose surface a droplet containing spores in suspension has 

 been spread with a zigzag stroke. B. Needle with flattened tip employed 

 to pick up disk of agar, bearing a spore, cut out by means of loop C. 

 D. Disk, with adhering spore transferred to slanted tube of agar. 



spread with a zigzag stroke over the surface of a hardened agar 

 plate, care being taken not to break the surface of the agar. In 

 this way most of the spores are brushed off at first, but toward 

 the end of the stroke a few remain. When these few germinate, 

 the colonies are discrete and may be transferred intact to fresh 

 media. 



If tubes of sterile water are available, a series of increasingly 

 less concentrated suspensions of spores can be made as a first 

 step in isolation by the dilution method. The proper amount of 

 dilution is entirely a matter of choice. A small quantity of inocu- 

 lum from the first tube should be placed in a tube of melted agar 

 cooled to about 45° C. The contents of this tube should be 



