SUGGESTED LABORATORY EXERCISES 431 



Consult the leader of the exercise or the instructor as to when the experi- 

 ment should be terminated. A portion of these data may be presented 

 in the form of a graph, plotting changes in pH against time for each 

 fungus and each medium. 



List of test fungi: Aspergillus rugulosus, Cephalofhecium roseum, Cerato- 

 stomella fimhriata, Glomerella cingulata, Monilinia fructicola, Neocosmo- 

 para vasinfecta, Penicillium spiculosporum, Penicillium expansum , Sordaria 

 fimicola, Sphaeropsis malorum, Phycomyces blakesleeanus (plus and 

 minus). 



EXERCISE 8 



Methods of Inoculating Agar Media and Their Effect upon Growth 



and Sporulation 



This is a brief and simple exercise, but it is outlined to demonstrate a 

 principle which seems to be fundamental, at least for certain fungi. The 

 most common way of inoculating agar media is to place a bit of actively 

 growing mycelium or a few spores at the center of the medium surface. 

 For most purposes this is entirely satisfactory, but in special cases other 

 methods may be used. A drop of spore suspension or of finely cut 

 mycelium may be placed at the center of the agar plate, or the entire 

 surface may be flooded with heavy spore suspension or suspension of cut 

 mycelium. The mycelium may be fragmented by cutting in a Waring 

 Blendor in 50 ml. of sterile water for 30 sec. to 1 min. 



For this exercise it is suggested that Petri dishes containing glucose- 

 asparagine-sucrose agar (such as the basal medium in Ex. 4) be used. 

 Fungi which ordinarily produce considerable mycelial growth before 

 fruiting abundantly may give the best results and will provide spore-free 

 inoculum when cultures are young. Some pycnidium-producing species 

 should be included. 



Each student should choose one or more fungi and inoculate plates in 

 triplicate by the following methods: 



A. A bit of mycelium placed at the center 



B. A few spores transferred by a needle placed at the center 



C. A drop of suspension of cut mycelium placed at the center. 



D. A drop of spore suspension placed at the center. 



E. Flooding the entire plate with suspension of cut mycelium 



F. Flooding the entire plate with a heavy spore suspension 



G. Diluting the spore suspension 1/1,000 and flooding the plate 



Observe the cultures daily and note the abundance of vegetative growth 

 and the time and abundance of sporulation in each case. 



List of test fungi: Alternaria sp., Ceratostomella fimhriata, Dendrophoma 

 ohscurans, Endothia parasitica, Fusarium sp., Glomerella cingulata, Guig- 

 nardia bidwellii, Helminthosporium sativum, Monilinia fructicola, Neo- 



