8 Introduction to Fungi [CH. 
In neither case can foreign organisms enter the 
culture. It is thus possible to grow a fungus free 
from all other organisms. If at first the culture 1s 
not pure a few spores of the required fungus may be 
transferred to a sterile medium and a pure culture so 
obtained. The mushroom fungus resembles those 
already examined in consisting of a mycelium and a 
part which bears the spores. The spawn contains a 
Fig. 6. Colonies of a fungus growing on gelatin in « Petri dish 
dense growth of hyphae which take up food from 
decaying matter and then produce the fructification 
known as a mushroom. 
If some of the white strands (i.e. mycelium) from 
mushroom spawn are placed in decaying manure or 
rich soil containing much organic matter, and kept 
moist and at a suitable temperature, mushrooms will 
be formed. If however the soil contains very little 
