196 
THE PLANT WORLD. 
puncture or wound in the skin, and then penetrates all the tissues 
of the fruit, eventually turning the whole into a rotten mass. 
General Nature of Fungi. 
It is not enough to know how a fungus acts in attacking a 
plant. While that is essential, it is by no means sufficient to en¬ 
able the teacher to suggest means for eradicating it. He must 
know how and when it reproduces itself. Now every fungus 
at some time in its life produces tiny seeds (spores) so small 
that they are easily carried by the wind for considerable dis¬ 
tances. No fungus comes spontaneously, any more than do weeds 
or grasses. Every one comes from a seed (in the broad sense) 
just as every tree comes from a seed. It is these minute seeds 
that blow from plant to plant, and from tree to tree, thus carry¬ 
ing the disease. Now it is a well established fact that every 
fungus is much more easily combated if taken when it first 
appears than after it gains full headway. It is with fungi as it 
is with weeds in your garden—you can kill them best when they 
are young, and it is a pretty difficult and tiresome thing to kill 
them after they are tall and pretty well rooted. It is important, 
therefore, that the grower of plants should know when and 
where the fungi begin their work on his trees and other plants, 
for this is the best time to spray with such a poisonous substance 
as “ Bordeaux Mixture ” in order to kill the largest number of 
fungi. Still another reason why we should quite certainly know 
when the fungi begin to grow is, that while we can kill them with 
a poisonous spray as long as they have not penetrated the tis¬ 
sues, when that is accomplished and they are safely inside of the 
leaf of the plant, it is quite useless to apply the poison. Here 
then is one of the most important points in this subject for the 
botanical teacher to know, and he should give as much time 
and thought to it as possible. 
Some Facts About Plant Diseases. 
Another thing to be remembered is that some plant diseases 
can be “ cured/' and many cannot. Thirst can be cured if the 
trouble is in the soil, and the roots are sound. So starvation can 
