FLORIDA STATE HORTICULTURAL SOCIETY 
61 
or potato, or what not, comes from a seed 
or cutting that was produced by one of its 
kind. The recognition of this outside 
source for the very beginnings of any fun¬ 
gus infection is of first importance in dis¬ 
ease control, whether by spraying, or by 
other measures. Once established, the 
greater part of the fungus plant is buried 
below the surface of its host and feeds and 
grows there well protected from outside 
agencies. It is practically impossible to 
get rid of a fungus thus established with 
anything short of the ax, the pruning saw 
or the knife, and such implements may 
mean loss of valuable plant parts. In the 
case of the less destructive diseases, we 
may tolerate a certain amount of unpre¬ 
vented infection, and wage warfare 
against their further spread. Spraying, 
to be most effective, must begin before 
the first infections. 
Our corn seed, merely in contact with a 
fertile soil, would not grow into a plant 
without suitable conditions for growth, 
mainly moisture and warmth. Similar 
favoring conditions are needed for any 
fungus plant to become established. The 
crop of fungi in any season is influenced 
by variations in such conditions. 
The seeds of higher plants usually 
sprout while buried in the soil, and a por¬ 
tion of the plant in a few days emerges 
from it. The spores of fungi usually 
sprout where they happen to lie on the 
surface of plant parts, in such chance 
films of moisture as rains or dews may 
furnish for a sufficient length of time. In¬ 
stead of a few days, as for seeds, the time 
for spore germination is a matter of a few 
hours, or very seldom of more than one 
or two days. The fungus, during a few 
hours more, may penetrate beneath the 
surface, either by actively dissolving a 
way through the plant’s protective layer 
of epidermis, or by entering one of the 
natural breathing-pore openings, or 
through some accidental wound. Most 
of the growth is below the surface. The 
microscopic parasite must affect a rather 
extensive area before its presence can be 
detected with the unaided eye. This 
takes, as a rule, several days to several 
weeks, referred to as the incubation 
period. So when the effects of a fungus 
are visible in considerable degree, we may 
feel sure that the start was really made 
some time before, and there may be as 
many or more incipient infections already 
truly established on neighboring parts of 
the host, certain to become apparent at the 
end of their incubation period. Once 
again, the key to success in spraying is 
protection against the very earliest of 
these infections. And how? By coating 
the parts to be protected with a suitable 
chemical that will either kill fungus 
spores in contact with it, or prevent them 
from germinating, or kill the tender 
growth from the spore before it can pene¬ 
trate the host tissues. The general ef¬ 
fect is the same in any case: the poison¬ 
ous spray material preventing the fung¬ 
ous growth. 
One serious limitation is when the 
spores are carried safely past a protec¬ 
tive spray coating and introduced directly 
into the deeper plant tissues on the 
mouthparts of some sucking or biting 
insect. It is a difficult case of undermin¬ 
ing defences, and unfortunately we are 
not yet able to cope absolutely with all 
