CHAPTER VIII 



MOULDS, YEAST, BACTERIA 



MOULDS occur on all sorts of organic substances bread, jam, 

 cheese, fruits, leather, blacking, horse-dung, etc. If you put 

 a slice of stale bread in a dish, cover it with a glass, and keep 

 it moist, various moulds will appear, three of which are easily 

 distinguished. One of the first of these, seen about the fourth 

 day, is the Black Mould (Mucor\ consisting of a white, fluffy 

 mass of fine threads which branch copiously on and in the bread. 

 From this mass there arise upright, stouter branches, each of 

 which ends in a round head, white at first, but soon turning 

 black. The head is a kind of spore case ; on dipping one into 

 water on a glass slide the spores are seen to escape by the burst- 

 ing of the case. Green and blue moulds and many other fungi 

 can be obtained by simply keeping soaked bread under a bell-jar, 

 but ultimately they are destroyed by bacteria, some of which 

 form slimy masses of various colours blood-red, purple, etc. 

 A host of fungi of all sorts can be obtained on dung treated in 

 this way moulds, other moulds growing as parasites on the 

 first ones, cup fungi, toadstools, etc. 



Mould-like fungi also grow on various living plants and 

 animals as parasites, often causing disease and death. In 

 autumn dead flies are often seen surrounded by a fluffy mass 

 of fungus threads, at the edges of which one can see, with a lens, 

 the spores which spread the fungus to other flies. A similar 

 growth of fungus threads is sometimes seen on goldfish which 

 have been neglected, and a fungus of the same kind attacks 

 salmon and does a great deal of damage. Almost every cul- 

 tivated plant is subject to one or more of the many destructive 

 fungus enemies of agriculture and gardening. Many -of these 

 fungi rusts, smuts, mildews, etc. are too small to be studied 



