48 Mildews [CH. 
considering in the present chapter are spoken of as 
Powdery or True Mildews. 
The true mildews comprise a large number of 
different species. One of the commonest and also one 
which will serve as an example of the group is the 
well-known mildew of grasses and cereals, Hrysiphe 
graminis, We shall have little difficulty in finding 
specimens of this disease in cornfields during the 
Si, i oe 
tee a rl 
Fig. 16. Wheat plant attacked by Erysiphe graminis. 
spring, especially if the weather has been dull or wet. 
In drier seasons it may be found in the shady and damp 
parts of the field. The leaves of a mildewed plant are 
covered with a white, a dirty white, or a pinkish 
powdery substance. It was to this that the term 
mildew was first applied, the leaves having the appear- 
ance of being dusted with some kind of powder (see 
Fig. 16). 
