ACOTYLEDONS FTTXGI LICHEES DIAGRAM 18. 



213 



There are many kinds of fungi similar 

 to mould, but still smaller, which are in- 

 visible to the naked eye, and can only be 

 detected by their ravages. The oidium 

 which attacks the vine is a fungus of this 

 description ; and the disease called mus- 

 cardine which attacks silkworms, is caused 

 by another ; the potatoe disease is either 

 caused, or frequently accompanied by, a 

 similar fungus ; another produces a 

 disease called fumagine in the olive ; and 

 yet others produce mildew, smut, and 

 ergot, in cereals. The ergot chiefly 

 attacks rye, when instead of the ordinary 

 grain, "we see large black horny grains 

 developed, shaped something like a cock's 

 spur. Ergot is poisonous, but is of great 

 use in medicine. Man himself is subject 

 to diseases caused by the presence of 

 fungi of this kind, such as the thrush and 

 ringworm. In the thrush, the white points which form on the 

 tongue and inside the mouth of children, are caused by the pre- 

 sence of a fungus. In the ringworm it-is also a fungus which 

 form the yellow crusts shaped like buttons, hollow in the middle, 

 which grow at the roots of the hair. 



We may add that the yeast which we have mentioned as 

 found in beer vats is also a fungus of this kind. 



Ergot ofJRye 



FAMILY OF LICHENS- 



The lichens resemble fungi, but instead of being moist, like the 

 latter, are dry. They often resemble parchment, and we should 

 scarcely take them for living plants if we did not see them grow 



