36 
FLORIDA STATE HORTICULTURAL SOCIETY 
tree where the actual food is prepared. 
The actual foods are starches, sugars and 
proteins. 
The tree prepares its own food. In 
the preparation of its food it uses the 
carbon and oxygen from the carbon di¬ 
oxide of the air; hydrogen and oxygen 
from water; and phosphorus, nitrogen 
and sulphur from the soil. The carbon, 
hydrogen and oxygen are combined to 
form starches and sugars. The energy 
for doing this work is derived from sun¬ 
light, and the work is done by small green 
bodies known as chloroplasts that are 
held in the living matter of certain plant 
cells. The green color you see in your 
trees is due to the green pigment con¬ 
tained in these small bodies. Leaves are 
frenched or yellowed when this green 
pigment is lacking in these bodies. 
The proteins are formed in various 
parts of the tree by the addition of phos¬ 
phorus, nitrogen and sulphur to the 
starches and sugars. You may ask, 
“What does the tree do with the tons of 
potash which we apply to our soils?” The 
tree still has some secrets hidden from us. 
We know that potassium, 'calcium, mag¬ 
nesium and iron are indispensable food 
materials. They are helpers in the work 
of the preparation, movement, storage 
and assimilation of the foods and the dis¬ 
posal of the by-products, and are not 
constituents of the living matter. But 
the details of how they help are for the 
most part lacking. 
After the foods are prepared, they are 
carried to different parts of the plant 
body where they are either used or stored 
for future use. 
Next, the tree grows. In growth, 
the tree makes use of the energy and ma¬ 
terials supplied by respiration, transpira¬ 
tion and nutrition. 
The tree has the power of response 
to irritation. It responds to the influence 
of such external stimuli as light, gravity, 
contact, etc. 
And finally, it has the power of repro¬ 
duction. This function gives the fruit 
which is the aim of our work in the grove. 
These functions of the tree— respira¬ 
tion, transpiration, nutrition, growth, ir¬ 
ritation and reproduction are the ones 
that are influenced by the external condi¬ 
tions which we have discussed, namely 
food, water, heat, light, freedom and soil. 
It is by the. close co-ordination of these 
functions and conditions that the tree 
lives, grows and produces fruit. For 
example, when we apply a normal fertili¬ 
zer to the soil, the tree responds to feed¬ 
ing if there is sufficient moisture in the 
soil, if the temperature is not too low, 
and if tree is not badly injured from dis¬ 
ease. The response of the tree to fer¬ 
tilizers therefore depends upon the other 
conditions contributing to growth being 
good. If any one of them is entirely off, 
results are not obtained from the fertili¬ 
zation. 
The tree growing in the wild is sub¬ 
ject to all of these conditions and it 
survives or perishes according as bene¬ 
ficial or detrimental conditions prevail. 
But in growing a tree under cultivation 
we endeavor to control the growth condi¬ 
tions by certain methods. The methods 
of control we use are those practices we 
carry out in the grove, which are: fertili¬ 
zation, cultivation, irrigation, drainage, 
orchard heating, pruning, spraying, fumi- 
