34 
FLORIDA STATE HORTICULTURAL SOCIETY 
what I refer. It is because nitrogen, 
potassium, phosphorus and calcium are 
not present in our soils in sufficient 
quantities for the requirements of the 
trees, so that we have to supply them 
in 'the form of different sources of 
ammonia, potash, phosphoric acid and 
lime. Of the other food elements, car¬ 
bon, hydrogen and oxygen are obtained 
from air and water, and there is al¬ 
ways a sufficient amount present for 
the proper development of the tree. 
The magnesium, iron and sulphur are 
obtained from the soil and are usually 
present in sufficient amounts in the 
soil, or they are contained in the dif¬ 
ferent fertilizers we use, so we do not 
concern ourselves about these. 
Next, as everyone knows, the tree 
must have water, by means of which 
the food materials are obtained from 
the soil and transferred from place to 
place within the plant body. Water is 
also the medium for chemical action 
and for the storage of substances with¬ 
in the cells. It is a part of the ground¬ 
work of all living things. 
As a living organism, the tree re¬ 
quires a certain amount of heat for the 
proper action of the living processes 
that go within its body, whereby it may 
manufacture, use and store its food, 
and utilize its energy for growth and 
reproduction. 
It also requires light, for this is its 
source of energy for doing its work. 
The light is absorbed by the green 
chlorophyll bodies, converted into 
chemical energy and stored in chemical 
compounds to be used in carrying on 
the work of the tree. 
The tree must also have proper free¬ 
dom, not only from diseases induced 
by insects and fungi, but also from 
razor-back hogs and tick-infested cat¬ 
tle. 
These conditions— food, water, heat, 
light and freedom —are those which 
are absolutely necessary for the main¬ 
tenance of life in the tree. 
In addition, there are other condi¬ 
tions which we recognize as of im¬ 
portance. Although they are not of 
absolute importance to the mere main¬ 
tenance of life, they are of import¬ 
ance for the development of trees on 
a commercial scale. There is the soil 
which is the medium for holding the 
tree in place, and from which the min¬ 
eral food materials and water are ob 
tained. In it profound chemical pro¬ 
cesses are constantly going on where¬ 
by certain plant foods become avail¬ 
able for absorption by the tree, and 
others are stored in non-available form 
so that they are not lost through wash¬ 
ing and leaching. 
In the soil are also contained hum¬ 
us and other organic materials. These 
improve the physical condition of the 
soil and enable it to hold more mois¬ 
ture and plant food, and are them¬ 
selves plant foods under certain con¬ 
ditions. In addition they serve to sup¬ 
port a rich growth of fungi and bac¬ 
teria. which are so important for mak¬ 
ing the plant foods available in the soil, 
especially the nitrogenous foods. 
As was said in the beginning, each 
of these conditions contributes to the 
growth of the tree. Therefore from 
the standpoint of controlling* these con- 
