380 



MOULDS AND YEASTS 



of Penicillium are known, the following being, perhaps, 

 the most important : 



(i) P. glaucum, Brefeld. This species is found on 

 bread, jam, fruit, and almost all kinds of decaying 

 organic material ; to its presence are due the character- 

 istic blue veins in a ripe Stilton or Dorset cheese. 



FIG. 51. A common " mould," Penicillium glaucum, Bref. h Hyphse form- 

 ing part of its mycelium ; a erect hypha bearing conidia c in chains, b 

 detached conidia, at s germination of a conidium has taken place, ^germ- 

 tube, the beginning of a new mycelium. (Enlarged 500 diameters.) 



The mycelium and hyphae in a young state are white and 

 cotton-like ; later, when the conidia are formed, the 

 fungus becomes a greenish-blue colour. 



The sterigmata are from 8 to 1 3 ^ long and 3 to 4 /a 

 broad. The conidia are round, smooth, and usually 

 from 3 to 4 /A in diameter, with a greenish tinge. 



