in Oats and Barley. 
403 
j1. sirigosa is not liable to the attack of the common oat- 
smut, for, gro'vvn under these conditions, it was as liable to 
become aflfected as any other variety. 
It is seen from the table that in 1885 sis varieties were free 
from smut. This was because thev were grown for the first time 
on the Experimental Farm, and from healthy seed. The other 
varieties had been gi'own for many years. "\Ye notice that in the 
22 varieties the disease has not failed to transmit itself in a 
single instance, and upon the whole in an increasing scale. 
The main question before us, however, is. In what manner 
does the propagation of smut take place ? To answer this 
we must take cognisance of the following facts : — ■ 
1. The spores of smut ripen and become diffused in the 
fields of themselves while the corn is growing, unlike the spores 
of bunt, which remain enclosed inside the kernel untU this 
is ripe. 
2. The diffusion of smut spores is most profuse Just after 
the ears have appeared ; hence it is most likely that this is the 
most favourable period for the propagation of the fungus. 
3. Since we have seen that spores simply adhering to the 
exterior of the grain do not to any appreciable extent cause the 
infection of the crop, it follows that this must take place by 
means of those spores which succeed in entering the space 
between the " cosh or husk and tbe kernel. 
4. As the kernels of oats and barley are tightly embraced by 
the husk, except where the husk opens to allow the stamens to 
protrude, it follows that this period is the most favourable for the 
infection of the grain. This is supported by the fact that the 
greatest number of smut spores are given off at the time the ears 
are flowering ; and it should be observed that at this period the 
spores fasten in great quantities on the viscid pistils, to which, 
of course, the spores have as easy access as the pollen has. 
The question presents itself, Does the com become infected 
by the spores which are inside the husk germinating directly 
and sending a mycelial hypha or thread into the ovaiy, or into 
the grain, while it is still green and soft ? In which case the 
presence of the fungus does not produce any observable effect 
until the grain germinates in the ensuing spring. Or do the 
spores, having gained admission into the husk, remain there 
quiescent until the grain germinates ? 
I was unable absolutely to decide this question for some 
time; but my experiments in the summer of 1887 clearly 
pointed to the last-named as being the most probable explana* 
tion. It is certain, however, that infection . takes place from 
within the husk, and not from without. • This is further shown 
