f 
540 
The illustration shows two patches of wheat-leaves sprayed 
with the fungicide known as ammonia-carbonate of copper—that 
is, carbonate of copper dissolved in dilute ammonia. Afer a plant- 
has been sprayed with this solution, the diluted ammonia evapor 
ates and leaves the carbonate of copper in the shape of an exceed- 
ingly fine powder. Consequently, when we examine the surface 
of the sprayed plant with the microscope, we instantly notice this 
deposit distributed in patches, as shown in the adjacent illustration, 
Each patch of deposit is a dried-up droplet of the spray ; about 
twenty such patches are shown in one illustration. Between the 
patches is seen that part of the wheat-leaf which was not hit by 
the spray. As long as the patches of poison remain they consti- 
tute a protection against the infection by means of spores, which 
may fall upon a sprayed leaf. A spore falling upon the poison will 
be killed as soon as it attempts to germinate. Even should it fall 
upon a portion of the leaf where there is no poison, growth may 
yet be prevented, as will be readily understood by examining the 
illustration, where the germination of spores c, d, e, and / has been 
checked, because their sprouts have run against the poison 
In the above ilustration a careful drawing is given of two 
different sprayings. In one case the leaf was sprayed for nine 
consecutive seconds ; in the other case, also for nine seconds, but at 
three different times of three seconds each, the leaf having dried 
between times. The results are very different. Where the spray 
was applied nine seconds continuously the drops have melted into 
one another, and left wide unprotected blanks amongst them (B). 
It is evident therefore, that Fig. A represents a more efficient method 
of spraying than B, not because more poison has been applied, 
but because it is in a finer state of sub-division. It will be seen at 
once that if the spores a, b, c, d, e, f, g, h had fallen on A instead 
of B their chance of growing would have been much diminished. 
