DISEASES OF PLANTS 
Organs Have Become Permanent 
Whatever may have been the causes 
of variation in plants, the facts remain 
that they are variously adapted, and 
that these adaptations are suited to all 
the conditions common on the surface of 
the earth. This has made necessary or- 
gans that mark them as different, per- 
forming different functions in different 
degrees, and these differences have be- 
come permanent. Therefore, unless these 
permanent likes and dislikes are consid- 
ered, the wants growing out of them sup- 
plied and they are protected from that 
which they dislike, there cannot be a 
condition of health. For this reason it is 
necessary to study the nature of the 
organism and the nature of the environ- 
ment It is only by this means that it 
can be determined whether they are 
adapted to each other, or whether the 
soil, climate and general surroundings 
contain injurious elements. If a certain 
soil, for instance, contained all that was 
necessary to the health of a tree, but if 
at the same time it contained something 
injurious, the tree would suffer; as in the 
case of a man who ate a good healthful 
meal containing all that was necessary to 
his vigor, but at the same time took poi- 
son. Again, it is often true that certain 
chemical qualities in the soil are good 
in certain proportions, but taken in larger 
portions become injurious. This is true 
of alkali salts, which in a certain degree 
are fertilizers, and stimulate the growth 
and vigor of fruits and other crops, but in 
larger quantities, become injurious. In 
certain excessive quantities they kill the 
little hairs that form on the roots and 
which gather the food substances in solu- 
tion, thus causing a lack of nourishment 
and final death of the plant. The symp- 
toms are generally a yellowing of the 
leaves. If we may judge by the unfavor- 
able conditions under which plant life has 
been observed to grow, we might conclude 
that there is life potentially in every par- 
ticle of earth, air and water. In other 
words, that life is everywhere, and that it 
strives to clothe itself with whatever 
forms are adapted to its surroundings. 
Whoever has observed the growing of 
889 
moss on the rocks in the desert or on a 
marble slab in a cemetery, must have 
wondered at the tenacity with which life 
struggles to maintain itself, and with 
which it strives to adapt itself to the 
most unfavorable conditions. Yet, it 
would be folly to plant a tree in the solid 
rock or try to grow a garden on a marble 
slab. We must, if we succeed, study the 
nature of the organism and the environ- 
ment. 
Health the Normal Condition 
Whatever may be the cause or causes 
of diseased conditions in plants, we are 
forced to the conclusion that the ten- 
dency of life is toward health and toward 
a more perfect expression of its being. 
Among the many proofs that may be of- 
fered are the following: 
First. The tendency of all plants to 
change, in order to become adapted to 
different conditions of soil, climate and 
whatever environment affects them. 
Second. The effort to repair any injury 
that has been done by insects, animals, 
wounds, diseases or from whatever 
cause. 
Diseases Classified 
We give herewith a general outline un- 
der which diseases may be classified. 
1. Secretional diseases, in which cel- 
lulose is transformed into gum, resin, 
manna. The effect is produced by over- 
action of the normal functions. 
2. Diseases produced by fungi 
other vegetable parasites. 
3. Diseases produced by decomposition, 
as gangrene, or canker. These are pro- 
cesses of decay in which the cellulose is 
transformed into a muddy fluid, a brown 
powder, or a carbonaceous mass. 
4. Diseases produced by the attack of 
insects and other animals. 
5. Atmospheric conditions. 
6. Soil and moisture conditions. 
7. Light, electricity, winds and storms. 
8. Crowding so that the food supply is 
cut off. 
9. Isolation and consequent lack of fer- 
tilization. 
10. Unknown causes. 
GRANVILLE LOWTHER 
and 
