FLORIDA STATE HORTICULTURAL SOCIETY. 
125 
Early in the 17th century van Helmont 
undertook to solve the problem of plant 
growth and proved to his satisfaction that 
all the products of plant growth were de¬ 
rived from water. 
Some fifty years later Digby (1660) 
attributed the growth of plants to a kind 
of “Balsam” which the air contained. 
A theory advanced later by Jethro Tull 
was to the effect that the food of plants 
consisted of soil particles and that these 
soil particles must be rendered very min¬ 
ute before they could be absorbed by the 
rootlets. This theory is of interest since 
the importance of good tillage is empha¬ 
sized in crop production. 
The first contribution of importance to 
the subject of plant nutrition was made 
by a Swiss naturalist, Bonnet, during the 
18th century. He found that air is the true 
source of carbon which forms so large 
a part of the plant substance. 
The first work written in the English 
language on Agricultural Chemistry was 
in 1795 by a Scottish Nobleman, the Earl 
of Dundonald. His teachings were that 
plants ‘are composed of grass with a small 
proportion of calcareous matter.” 
DeSaussure in 1804 gave to the world 
the most important contribution to science 
up to this time. He was the first to call 
attention to the mineral or ash constitu¬ 
ents of plants and maintained that these 
ash ingredients were essential, for with¬ 
out them plant life was impossible. 
* 
In the early part of the last century 
Sir Humphry Davy published a series of 
lectures on Agricultural Chemistry which 
added to the knowledge of the composi¬ 
tion and functions of the soil. 
Boussingault in 1838 was the first 
chemist to carry out elaborate experi¬ 
ments to determine the question whether 
plants could assimilate the free nitrogen 
of the air. 
It was not until 1840 when Liebig pub¬ 
lished his celebrated work “Organic 
Chemistry in Its Application to Agricul¬ 
ture and Physiology” that the new science 
of Agriculture was inaugurated. In his 
preface he states that “perfect agriculture 
is the true foundation of all trade and in¬ 
dustry, but a rational system of agricul¬ 
ture cannot be formed without the appli¬ 
cation of scientific principles, for such a 
system must be based on an exact ac¬ 
quaintance with the means of nutrition 
of vegetables and with the influence of 
soils and actions of manures upon them. 
This knowledge we must seek from chem¬ 
istry which teaches the mode of investi¬ 
gating the composition and of studying 
the character of the different substances 
from which plants derive nourishment.” 
Chemistry tells us that the materials of 
which all matter is composed consist of 
some seventy distinct elementary forms 
of matter known as chemical elements. 
It is by means of chemical analysis that 
we are able to determine the elementary 
composition of the earth and its life. 
Less than one hundred years ago it was 
learned that plants are built up from ma¬ 
terials from the air and soil, water being 
one of them. The number and kind of 
elements that have been found to be ab¬ 
solutely essential to the growth of plants 
are ten—carbon, oxygen, hydrogen, nitro¬ 
gen, phosphorus, potassium, calcium, 
magnesium, sulphur and iron. These are 
called plant food elements and all healthy 
plants must contain them, and' in the ab¬ 
sence of one of them, the plant cannot 
make a normal growth. 
