OUR COMMON MOULDS. 



405 



With the spores of this mould repeated sowings have been made, 

 with gratifying results. When a slice of fresh bread was placed in 

 the bell-jar and certain marked places were sprinkled with spores by 

 means of a pair of forceps, in the course of twenty-six hours those spots 

 sown were covered with the young mould, while all other places were 

 entirely free from it. In one case a fresh slice of bread was wrapped in 

 a piece of paper, with the exception of a star-shaped figure cut from the 

 paper, which came in the middle of the slice. Over the whole a slice 

 of mouldy bread was shaken so gently that no spores were seen to 

 fall; the paper was then carefully removed, and the bread placed under 

 the bell-jar. After the xisual time a fine star of blue mould made its 

 appearance, soon spreading over the whole of the bread. One could 

 as easily write his name in mould on bread as with clover-seed upon 

 the soil, though it would not be as enduring an inscription. 



It seems difficult for some people to see how the spores of these 

 various moulds can exist almost everywhere, ready to grow when the 

 first opportunity offers itself. With the hope of making this matter 

 appear clearer, the following calculations have been carefully made : 

 The blue mould (Penicillium crustaceum) is very favorable for the esti- 

 mation of the number of spores produced, as the heads are quite open, 

 and the spores are naked and distinct. 



Pig. 8. TRicoTnEcirsi roseum. Fr. 



A piece of decaying apple was selected, because the mould can be 

 removed from that portion covered with the smooth skin without be. 

 ing mixed with foreign matter. When the mould was still young and 

 no spores had fallen away, it was viewed with the high power of the 

 microscope. There were usually twenty filaments to each head, and 

 twenty spores on a filament, or 4,000 spores to a head or single stalk. 



