110 A MANUAL OF BACTERIOLOGY 



Exercise 152. Study of Penicillium 



The common green mold, Penicillium, is one of the most 

 cosmopolitan of the fungi. Its spores are found nearly every- 

 where, and it grows upon anything from lemons to old boots. 



Penicillium is a fungus genus belonging to the Ascomycetes. 

 The perithecia are, however, quite rare in the more common species. 

 The spores formed are therefore mostly of the conidial type. 



The green Penicillium is usually abundant in portions of the 

 home where food is kept, and causes the loss of much stored 

 food. In the fruit business serious losses are caused by Penicillia, 

 which attack oranges, lemons, apples, cherries, peaches, etc., 

 especially if shipments are made over long distances in warm, 

 muggy weather. In breweries Penicillium may cause great 

 damage to the malt, as well as to the finished beer. 



Grapes on which this mold is abundant make defective wines. 

 The mold not only destroys the necessary sugars, but forms 

 waste products which are deleterious to the subsequent growth 

 of the yeasts. 



Some species of Penicillium, like P. Camemberti, play a useful 

 role in the ripening of cheeses. 



1. Examine a culture of Penicillium and note 



a. The general appearance of the whole mass. 



b. The position and direction of the threads with reference 



to the supporting substratum. Remove a small tuft 

 of these aerial hyphse, place them in a drop of 50 

 per cent alcohol on a slide, tease apart carefully, and 

 examine with both low and high powers. 



2. The conidiophores are the straight aerial branches, each of 

 which ends in a tuft of spore-bearing branches. Are cross walls 

 present ? Do all the branches reach to about the same level ? 

 How many series of branches are present ? At the distal end 

 note the sterigmata,' or club-shaped cells, which bear the spores. 



3. The spores arise in basipetal order from the sterigmata, 

 Are spores relatively few or abundant ? What is their shape ? 

 color? Is the spore wall thickened? Do the spores contain 

 protoplasm? oil? vacuoles? 



