4.6 . DIRECTIONS FOR 



be always found one or more members able to 

 exhibit this instrument, and others would soon 

 learn its use. Ministers might sometimes 

 attend at such meetings, and would find reveal- 

 ing the secrets of nature no unworthy or inef- 

 fectual step towards awakening attention to the 

 more weighty objects of their sacred calling. 

 The author has more than once shown these 

 corn diseases to the members of a farmers' 

 club, who viewed them with extreme interest. 

 Nothing can be more simple. To show the 

 puccinia graminisy or mildew of the wheat, the 

 exhibitor should first strip off lengthwise a 

 little bit of the affected straw, and let it be 

 viewed as an opaque object. The thick cluster- 

 ing of the spores, as delineated in the first 

 drawing of this chapter, might be easily pointed 

 out, as well as the way in which they rupture 

 the cuticle : an half-inch achromatic object-glass, 

 with a low eye-piece, will sufiice for this ; with 

 a higher power, and bits of cuticle and straw, 

 cut so thin that the light may easily be shown 

 through them from the mirror, the stomata 

 would be seen, and the vegetation of the spores 

 on the mycelium in the cavities beneath them. 

 Lastly, a small piece of one of the dark patches 

 might be taken off with the point of a pin or 



