76 Smuts [CH. 
the case of group A the spores are sown with the 
grain. Conditions which favour the germination of 
the oats and barley apparently favour the germina- 
tion of the spores. The secondary spores formed 
from these produce germ tubes which make their way 
into the shoots of the seedling plants. It has been 
shown that the fungus can only obtain an entry into 
the plant at a very young stage. When the leaves 
have pushed their way through the leaf sheaths the 
shoots become hardier and spores cannot enter. 
On entering the plant the germ tube, or as it is 
now called the mycelium, makes its way to the growing 
point of the shoot. It takes its food from the cells of 
the plant but does not kill them as in the case of the 
potato disease; consequently there are no external 
signs that the plant is being attacked. As the oat 
grows in the spring the mycelium grows with it and 
is to be found in the region of the growing point, but 
not in the older parts of the plant. By maintaining 
its position at the growing point it is able to pass out 
into the new shoots as these are all formed there. 
In this way all the flowering shoots of the attacked 
plant are usually infected and practically all the 
grains of an infected ear are smutted. 
When the plant is supplying the grain liberally 
with food stuff and so causing it to swell the mycelium 
grows rapidly and a dense network is formed within 
the grain. The spores are formed inside the tubes of 
the mycelium and set free as a powder. 
The loose smut'of wheat appears at the time of 
flowering. The coverings which enclose it burst about 
this time and the black spores are blown about by the 
wind or washed to the ground by rain. Soon nothing 
